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Postgres FD Implementation
Commit 3733bd46 authored by Thomas G. Lockhart's avatar Thomas G. Lockhart
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First version of files from Oliver Elphick.

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doc/src/sgml/ref/commands.sgml
View file @ 3733bd46
......@@ -16,6 +16,10 @@
&createFunction;
&createIndex;
&createLanguage;
&createOperator;
&createRule;
&createSequence;
&createTable;
&dropFunction;
&select;
......
doc/src/sgml/ref/create_operator.sgml 0 → 100644
View file @ 3733bd46
<REFENTRY ID="SQL-CREATEOPERATOR-1">
<REFMETA>
<REFENTRYTITLE>
CREATE OPERATOR
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
CREATE OPERATOR
</REFNAME>
<REFPURPOSE>
Defines a new user operator.
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE OPERATOR <replaceable>name</replaceable>
([ LEFTARG = <replaceable class="parameter">type1</replaceable> ]
[, RIGHTARG = <replaceable class="parameter">type2</replaceable> ]
, PROCEDURE = <replaceable class="parameter">func_name</replaceable>
[, COMMUTATOR = <replaceable class="parameter">com_op</replaceable> ]
[, NEGATOR = <replaceable class="parameter">neg_op</replaceable> ]
[, RESTRICT = <replaceable class="parameter">res_proc</replaceable> ]
[, HASHES ]
[, JOIN = <replaceable class="parameter">join_proc</replaceable> ]
[, SORT = <replaceable class="parameter">sort_op</replaceable> [, ...] ]
)
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATEOPERATOR-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">name</replaceable>
</TERM>
<LISTITEM>
<PARA>
The name of an existing aggregate function.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">type1</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">type2</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">func_name</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">com_op</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">neg_op</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">res_proc</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">join_proc</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<replaceable class="parameter">sort_op</replaceable>
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATEOPERATOR-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>CREATE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if the operator is successfully created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-CREATEOPERATOR-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<PARA>
This command defines a new user operator, operator_name.
The user who defines an operator becomes its owner.
</para>
<para>
The operator_name is a sequence of up to sixteen punctua
tion characters. The following characters are valid for
single-character operator names:<literallayout>
~ ! @ # % ^ & ` ? </literallayout>
</para>
<para>
If the operator name is more than one character long, it
may consist of any combination of the above characters or
the following additional characters:<literallayout>
| $ : + - * / &lt; &gt; =</literallayout>
</para>
<para>
The operator "!=" is mapped to "&lt;&gt;" on input, and they are
therefore equivalent.
</para>
<para>
At least one of leftarg and rightarg must be defined. For
binary operators, both should be defined. For right unary
operators, only arg1 should be defined, while for left
unary operators only arg2 should be defined.
</para>
<para>
The name of the operator, operator_name, can be composed
of symbols only. Also, the func_name procedure must have
been previously defined using create function(l) and must
have one or two arguments.
</para>
<para>
The commutator operator is present so that Postgres can
reverse the order of the operands if it wishes. For exam
ple, the operator area-less-than, >>>, would have a commu
tator operator, area-greater-than, <<<. Suppose that an
operator, area-equal, ===, exists, as well as an area not
equal, !==. Hence, the query optimizer could freely con
vert:
<programlisting>
"0,0,1,1"::box >>> MYBOXES.description
</programlisting>
to
<programlisting>
MYBOXES.description <<< "0,0,1,1"::box</programlisting>
</para>
<para>
This allows the execution code to always use the latter
representation and simplifies the query optimizer some
what.
</para>
<para>
The negator operator allows the query optimizer to convert
<programlisting>
NOT MYBOXES.description === "0,0,1,1"::box
</programlisting>
to
<programlisting>
MYBOXES.description !== "0,0,1,1"::box
</programlisting>
</para>
<para>
If a commutator operator name is supplied, Postgres
searches for it in the catalog. If it is found and it
does not yet have a commutator itself, then the commutator's
entry is updated to have the current (new) operator
as its commutator. This applies to the negator, as well.
</para>
<para>
This is to allow the definition of two operators that are
the commutators or the negators of each other. The first
operator should be defined without a commutator or negator
(as appropriate). When the second operator is defined,
name the first as the commutator or negator. The first
will be updated as a side effect.
</para>
<para>
The next two specifications are present to support the
query optimizer in performing joins. Postgres can always
evaluate a join (i.e., processing a clause with two tuple
variables separated by an operator that returns a boolean)
by iterative substitution [WONG76]. In addition, Postgres
is planning on implementing a hash-join algorithm along
the lines of [SHAP86]; however, it must know whether this
strategy is applicable. For example, a hash-join
algorithm is usable for a clause of the form:
<programlisting>
MYBOXES.description === MYBOXES2.description
</programlisting>
but not for a clause of the form:
<programlisting>
MYBOXES.description <<< MYBOXES2.description.
</programlisting>
The hashes flag gives the needed information to the query
optimizer concerning whether a hash join strategy is
usable for the operator in question.</para>
<para>
Similarly, the two sort operators indicate to the query
optimizer whether merge-sort is a usable join strategy and
what operators should be used to sort the two operand
classes. For the === clause above, the optimizer must
sort both relations using the operator, <<<. On the other
hand, merge-sort is not usable with the clause:
<programlisting>
MYBOXES.description <<< MYBOXES2.description
</programlisting>
</para>
<para>
If other join strategies are found to be practical, Post
gres will change the optimizer and run-time system to use
them and will require additional specification when an
operator is defined. Fortunately, the research community
invents new join strategies infrequently, and the added
generality of user-defined join strategies was not felt to
be worth the complexity involved.
</para>
<para>
The last two pieces of the specification are present so
the query optimizer can estimate result sizes. If a
clause of the form:
<programlisting>
MYBOXES.description <<< "0,0,1,1"::box
</programlisting>
is present in the qualification, then Postgres may have to
estimate the fraction of the instances in MYBOXES that
satisfy the clause. The function res_proc must be a reg
istered function (meaning it is already defined using
define function(l)) which accepts one argument of the correct
data type and returns a floating point number. The
query optimizer simply calls this function, passing the
parameter "0,0,1,1" and multiplies the result by the relation
size to get the desired expected number of instances.
</para>
<para>
Similarly, when the operands of the operator both contain
instance variables, the query optimizer must estimate the
size of the resulting join. The function join_proc will
return another floating point number which will be multiplied
by the cardinalities of the two classes involved to
compute the desired expected result size.
</para>
<para>
The difference between the function
<programlisting>
my_procedure_1 (MYBOXES.description, "0,0,1,1"::box)
</programlisting>
and the operator
<programlisting>
MYBOXES.description === "0,0,1,1"::box
</programlisting>
is that Postgres attempts to optimize operators and can
decide to use an index to restrict the search space when
operators are involved. However, there is no attempt to
optimize functions, and they are performed by brute force.
Moreover, functions can have any number of arguments while
operators are restricted to one or two.
</PARA>
<REFSECT2 ID="R2-SQL-CREATEOPERATOR-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<PARA>
Refer to <citetitle>PostgreSQL User's Guide</citetitle> chapter 5
<comment>
This reference must be corrected.
</comment>
for further information.
Refer to DROP OPERATOR statement to drop operators.
</REFSECT2>
<REFSECT1 ID="R1-SQL-CREATEOPERATOR-2">
<TITLE>
Usage
</TITLE>
<PARA>The following command defines a new operator,
area-equality, for the BOX data type.
</PARA>
<ProgramListing>
CREATE OPERATOR === (
LEFTARG = box,
RIGHTARG = box,
PROCEDURE = area_equal_procedure,
COMMUTATOR = ===,
NEGATOR = !==,
RESTRICT = area_restriction_procedure,
HASHES,
JOIN = area-join-procedure,
SORT = <<<, <<<)
</ProgramListing>
</REFSECT1>
<REFSECT1 ID="R1-SQL-CREATEOPERATOR-3">
<TITLE>
Compatibility
</TITLE>
<PARA>
CREATE OPERATOR is a PostgreSQL extension of SQL.
</PARA>
<REFSECT2 ID="R2-SQL-CREATEOPERATOR-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<PARA>
There is no CREATE OPERATOR statement on SQL92.
</PARA>
</refsect2>
</refsect1>
</REFENTRY>
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Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
sgml-parent-document:nil
sgml-default-dtd-file:"../reference.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:"/usr/lib/sgml/catalog"
sgml-local-ecat-files:nil
End:
-->
doc/src/sgml/ref/create_rule.sgml 0 → 100644
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<REFENTRY ID="SQL-CREATERULE-1">
<REFMETA>
<REFENTRYTITLE>
CREATE RULE
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
CREATE RULE
</REFNAME>
<REFPURPOSE>
Defines a new rule.
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE RULE <replaceable class="parameter">name</replaceable>
AS ON <replaceable class="parameter">event</replaceable>
TO <replaceable class="parameter">object</replaceable> [WHERE <replaceable class="parameter">condition</replaceable>]
DO [INSTEAD]
[<replaceable class="parameter">action</replaceable> | NOTHING ]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATERULE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">name</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The name of a rule to create.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">event</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Event is one of <literal>select</literal>, <literal>update</literal>, <literal>delete</literal> or <literal>insert</literal>.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">object</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Object is either <replaceable class="parameter">table</replaceable> or <replaceable class="parameter">table</replaceable>.<replaceable class="parameter">column</replaceable>.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">condition</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Any SQL <literal>where</literal> clause. <literal>new</literal> or
<literal>current</literal> can appear instead of an instance
variable whenever an instance variable is permissible in SQL.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">action</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Any SQL-statement. <literal>new</literal> or
<literal>current</literal> can appear instead of an instance
variable whenever an instance variable is permissible in SQL.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATERULE-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>CREATE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if the rule is successfully created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-CREATERULE-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<PARA>
The semantics of a rule is that at the time an individual instance is
accessed, updated, inserted or deleted, there is a current instance (for
retrieves, updates and deletes) and a new instance (for updates and
appends). If the <replaceable class="parameter">event</replaceable>
specified in the <literal>on</literal> clause and the
<replaceable class="parameter">condition</replaceable> specified in the
<literal>where</literal> clause are true for the current instance, the
<replaceable class="parameter">action</replaceable> part of the rule is
executed. First, however, values from fields in the current instance
and/or the new instance are substituted for
<literal> current.</literal><replaceable class="parameter">attribute-name</replaceable>
and <literal>new.</literal><replaceable class="parameter">attribute-name</replaceable>.
</para>
<para>
The <replaceable class="parameter">action</replaceable> part of the rule
executes with the same command and transaction identifier as the user
command that caused activation.
</para>
<REFSECT2 ID="R2-SQL-CREATERULE-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<para>
A note of caution about SQL rules is in order. If the same class name
or instance variable appears in the
<replaceable class="parameter">event</replaceable>, the
<replaceable class="parameter">condition</replaceable> and the
<replaceable class="parameter">action</replaceable> parts of a rule,
they are all considered different tuple variables. More accurately,
<literal>new</literal> and <literal>current</literal> are the only tuple
variables that are shared between these clauses. For example, the following
two rules have the same semantics:
<programlisting>
on update to EMP.salary where EMP.name = "Joe"
do update EMP ( ... ) where ...
on update to EMP-1.salary where EMP-2.name = "Joe"
do update EMP-3 ( ... ) where ...
</programlisting>
Each rule can have the optional tag <literal>instead</literal>. Without
this tag, <replaceable class="parameter">action</replaceable> will be
performed in addition to the user command when the
<replaceable class="parameter">event</replaceable> in the
<replaceable class="parameter">condition</replaceable> part of the rule
occurs. Alternately, the
<replaceable class="parameter">action</replaceable> part will be done
instead of the user command. In this later case, the
<replaceable class="parameter">action</replaceable> can be the keyword
<literal>nothing</literal>.
</para>
<para>
When choosing between the rewrite and instance rule systems for a
particular rule application, remember that in the rewrite system,
<literal>current</literal> refers to a relation and some qualifiers
whereas in the instance system it refers to an instance (tuple).
</para>
<para>
It is very important to note that the rewrite rule system
will neither detect nor process circular rules. For example, though each
of the following two rule definitions are accepted by Postgres, the
retrieve command will cause Postgres to crash:
<example>
<title>Example of a circular rewrite rule combination.</title>
<programlisting>
create rule bad_rule_combination_1 is
on select to EMP
do instead select to TOYEMP
create rule bad_rule_combination_2 is
on select to TOYEMP
do instead select to EMP
</programlisting>
<para>
This attempt to retrieve from EMP will cause Postgres to crash.
<programlisting>
select * from EMP
</programlisting></para>
</example>
</para>
<para>
You must have rule definition access to a class in order
to define a rule on it (see change acl(l)).
<comment>
There is no manpage change or change_acl. What is intended?
</comment>
</PARA>
</REFSECT2>
</refsect1>
<REFSECT1 ID="R1-SQL-CREATERULE-2">
<TITLE>
Usage
</TITLE>
<PARA>
Make Sam get the same salary adjustment as Joe
<programlisting>
create rule example_1 is
on update EMP.salary where current.name = "Joe"
do update EMP (salary = new.salary)
where EMP.name = "Sam"
</programlisting>
At the time Joe receives a salary adjustment, the event
will become true and Joe's current instance and proposed
new instance are available to the execution routines.
Hence, his new salary is substituted into the action part
of the rule which is subsequently executed. This propagates
Joe's salary on to Sam.
</para>
<para>
Make Bill get Joe's salary when it is accessed
<programlisting>
create rule example_2 is
on select to EMP.salary
where current.name = "Bill"
do instead
select (EMP.salary) from EMP where EMP.name = "Joe"
</programlisting>
</para>
<para>
Deny Joe access to the salary of employees in the shoe
department. (<function>pg_username()</function> returns the name of
the current user)
<programlisting>
create rule example_3 is
on select to EMP.salary
where current.dept = "shoe" and pg_username() = "Joe"
do instead nothing
</programlisting>
</para>
<para>
Create a view of the employees working in the toy department.
<programlisting>
create TOYEMP(name = char16, salary = int4)
create rule example_4 is
on select to TOYEMP
do instead select (EMP.name, EMP.salary) from EMP
where EMP.dept = "toy"
</programlisting>
</para>
<para>
All new employees must make 5,000 or less
<programlisting>
create rule example_5 is
on insert to EMP where new.salary > 5000
do update newset salary = 5000
</programlisting>
</PARA>
</REFSECT1>
<REFSECT1 ID="R1-SQL-CREATERULE-3">
<TITLE>
Bugs
</TITLE>
<PARA>
<literal>instead</literal> rules do not work properly.
</para>
<para>
The object in a SQL rule cannot be an array reference and
cannot have parameters.
</para>
<para>
Aside from the "oid" field, system attributes cannot be
referenced anywhere in a rule. Among other things, this
means that functions of instances (e.g., "<literal>foo(emp)</literal>" where
"<literal>emp</literal>" is a class) cannot be called anywhere in a rule.
</para>
<para>
The rule system stores the rule text and query plans as
text attributes. This implies that creation of rules may
fail if the rule plus its various internal representations
exceed some value that is on the order of one page (8KB).
</PARA>
<REFSECT1 ID="R1-SQL-CREATERULE-4">
<TITLE>
Compatibility
</TITLE>
<PARA>
CREATE RULE statement is a PostgreSQL language extension.
</PARA>
<REFSECT2 ID="R2-SQL-CREATERULE-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<para>
There is no CREATE RULE statement in SQL92.
</para>
</refsect2>
</refsect1>
</REFENTRY>
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doc/src/sgml/ref/create_sequence.sgml 0 → 100644
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<REFENTRY ID="SQL-CREATESEQUENCE-1">
<REFMETA>
<REFENTRYTITLE>
CREATE SEQUENCE
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
CREATE SEQUENCE
</REFNAME>
<REFPURPOSE>
creates a new sequence number generator.
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE SEQUENCE <replaceable class="parameter">seqname</replaceable>
[INCREMENT <replaceable class="parameter">increment</replaceable>]
[MINVALUE <replaceable class="parameter">minvalue</replaceable>]
[MAXVALUE <replaceable class="parameter">maxvalue</replaceable>]
[START <replaceable class="parameter">start</replaceable>]
[CACHE <replaceable class="parameter">cache</replaceable>]
[CYCLE]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">seqname</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The name of a sequence to be created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">increment</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The <option>INCREMENT <replaceable class="parameter">increment</replaceable></option> clause is optional. A positive value will make an
ascending sequence, a negative one a descending sequence. The default value
is 1.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">minvalue</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional clause <option>MINVALUE
<replaceable class="parameter">minvalue</replaceable></option>
determines the minimum value
a sequence can be. The defaults are 1 and -2147483647 for
ascending and descending sequences, respectively.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">maxvalue</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Use the optional clause <option>MAXVALUE
<replaceable class="parameter">maxvalue</replaceable></option> to
determine the maximum
value for the sequence. The defaults are 2147483647 and -1 for
ascending and descending sequences, respectively.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">start</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional <option>START
<replaceable class="parameter">start</replaceable>
clause</option> enables the sequence to begin anywhere.
The default starting value is
<replaceable class="parameter">minvalue</replaceable>
for ascending sequences and
<replaceable class="parameter">maxvalue</replaceable>
for descending ones.
<comment>
What happens if the user specifies start outside the range?
</comment>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">cache</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The <option>CACHE <replaceable class="parameter">cache</replaceable></option> option
enables sequence numbers to be preallocated
and stored in memory for faster access. The minimum
value is 1 (no cache) and this is also the default.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>CYCLE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional CYCLE keyword may be used to enable the sequence
to continue when the
<replaceable class="parameter">maxvalue</replaceable> or
<replaceable class="parameter">minvalue</replaceable> has been
reached by
an ascending or descending sequence respectively. If the limit is
reached, the next number generated will be whatever the
<replaceable class="parameter">minvalue</replaceable> or
<replaceable class="parameter">maxvalue</replaceable> is,
as appropriate.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>CREATE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if the command is successful.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>ERROR: amcreate: '<replaceable class="parameter"> seqname</replaceable>' relation already exists</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
If the sequence specified already exists.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<PARA>
CREATE SEQUENCE will enter a new sequence number generator
into the current data base. This involves creating and initialising a
new single block
table with the name <replaceable class="parameter">seqname</replaceable>.
The generator will be "owned" by the user issuing the command.
</PARA>
<para>
After the sequence is created, you may use the function
<function>nextval()</function> with the
sequence name as the argument to get a new number from the sequence.
The function <function>currval('<replaceable class="parameter">sequence_name</replaceable>')</function> may be used
to determine the number returned by the last call to
<function>nextval()</function> for the
specified sequence in the current session.
</para>
<para>
Use a query like
<programlisting>
SELECT * FROM sequence_name;
</programlisting>
to get the parameters of a sequence.
</para>
<para>
Low-level locking is used to enable multiple simultaneous
calls to a generator.
</para>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<PARA>
Refer to the DROP SEQUENCE statement to remove a sequence.
</PARA>
<para>
Each backend uses its own cache to store allocated numbers.
Numbers that are cached but not used in the current session will be
lost.
</para>
</REFSECT2>
</refsect1>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-2">
<TITLE>
Usage
</TITLE>
<PARA>
Create an ascending sequence called serial, starting at 101:
</PARA>
<ProgramListing>
CREATE SEQUENCE serial START 101;
</ProgramListing>
<para>
Select the next number from this sequence
<programlisting>
SELECT NEXTVAL ('serial');
nextval
-------
114
</programlisting>
</para>
<para>
Use this sequence in an INSERT:
<programlisting>
INSERT INTO distributors VALUES (NEXTVAL ('serial'),'nothing');
</programlisting>
</para>
</REFSECT1>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-3">
<TITLE>
Compatibility
</TITLE>
<PARA>
CREATE SEQUENCE statement is a PostgreSQL language extension.
</PARA>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<PARA>
There is no CREATE SEQUENCE statement on SQL92.
</PARA>
</refsect2>
</refsect1>
</REFENTRY>
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<REFENTRY ID="SQL-CREATETABLE-1">
<REFMETA>
<REFENTRYTITLE>
CREATE TABLE
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
CREATE TABLE
</REFNAME>
<REFPURPOSE>
Creates a new table.
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE TABLE <REPLACEABLE CLASS="PARAMETER">table</REPLACEABLE> (
<REPLACEABLE CLASS="PARAMETER">column</REPLACEABLE> <REPLACEABLE CLASS="PARAMETER">type</REPLACEABLE> [DEFAULT <REPLACEABLE CLASS="PARAMETER">value</REPLACEABLE>] [CONSTRAINT <REPLACEABLE CLASS="PARAMETER">column_constraint</REPLACEABLE>] [, ...]
[, <REPLACEABLE CLASS="PARAMETER">column</REPLACEABLE> ...]
[, CONSTRAINT <REPLACEABLE CLASS="PARAMETER">table_constraint</REPLACEABLE>]
) [INHERITS ( <REPLACEABLE CLASS="PARAMETER">inherited_table</REPLACEABLE> [, ...] )]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATETABLE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">table</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
The name of a new table to be created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">column</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
The name of a column.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">type</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
The type of the column.
(Refer to the <ProductName>Postgres</ProductName> User's Guide for
further information about data types).
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">value</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
A default value for a column.
See the DEFAULT clause for more information.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">inherited_table</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
The optional INHERITS clause specifies a collection of table
names from which this table automatically inherits all fields.
If any inherited field name appears more than once, PostgreSQL
reports an error. PostgreSQL automatically allows the created
table to inherit functions on tables above it in the inheritance
hierarchy. Inheritance of functions is done according
to the conventions of the Common Lisp Object System (CLOS).
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">column_constraint</REPLACEABLE>
<REPLACEABLE CLASS="PARAMETER">table_constraint</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>
The optional CONSTRAINT clause specifies a list of integrity
constraints which new or updated entries must satisfy for
an insert or update operation to succeed. Each constraint
must evaluate to a boolean expression. Multiple columns
may be referenced within a single constraint.
See CONSTRAINT clause for more information.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATETABLE-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>status</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>CREATE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if table is successfully created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>ERROR</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if table creation failed.
This is usually accompanied by some descriptive text, such as:
<ProgramListing>
amcreate: "<replaceable class="parameter">table</replaceable>" relation already exists
</ProgramListing>
which occurs at runtime, if the table specified already exists
in the database.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-CREATETABLE-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<PARA>
CREATE TABLE will enter a new table into the current data
base. The table will be "owned" by the user issuing the
command.
<PARA>
The new table is created as a heap with no initial data.
A table can have no more than 1600 columns (realistically,
this is limited by the fact that tuple sizes must
be less than 8192 bytes), but this limit may be configured
lower at some sites. A table cannot have the same name as
a system catalog table.
</PARA>
<REFSECT2 ID="R2-SQL-DEFAULTCLAUSE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
DEFAULT clause
</TITLE>
<PARA>
<SYNOPSIS>
DEFAULT <REPLACEABLE CLASS="PARAMETER">value</REPLACEABLE>
</SYNOPSIS>
<PARA>
The DEFAULT clause assigns a default data value to a column.
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">value</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The possible values for expression are:
<itemizedlist>
<listitem>
<simpara>
a literal value
</simpara>
</listitem>
<listitem>
<simpara>
a user function
</simpara>
</listitem>
<listitem>
<simpara>
a niladic function
</simpara>
</listitem>
</itemizedlist>
</para>
</listitem>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>ERROR: DEFAULT: type mismatched</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
if data type of default value doesn't match the
column definition's data type.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
<PARA>
The DEFAULT clause assigns a default data value to a column
(via a column definition in the CREATE TABLE statement).
The data type of a default value must match the column definition's
data type.
</PARA>
<PARA>
An INSERT operation that includes a column without a specified
default value will assign the NULL value to the column
if no explicit data value is provided for it.
Default <replaceable class="parameter">literal</replaceable> means
that the default is the specified constant value.
Default <replaceable class="parameter">niladic-function</replaceable>
or <replaceable class="parameter">user-function</replaceable> means
that the default
is the value of the specified function at the time of the INSERT.
</PARA>
<PARA>
There are two types of niladic functions:<variablelist>
<varlistentry>
<term>niladic USER</term>
<listitem>
<variablelist>
<varlistentry>
<term>CURRENT_USER / USER</term>
<listitem>
<simpara>See CURRENT_USER function</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>SESSION_USER</term>
<listitem>
<simpara>not yet supported</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>SYSTEM_USER</term>
<listitem>
<simpara>not yet supported</simpara>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term>niladic datetime</term>
<listitem>
<variablelist>
<varlistentry>
<term> CURRENT_DATE</term>
<listitem>
<simpara>See CURRENT_DATE function</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>CURRENT_TIME</term>
<listitem>
<simpara>See CURRENT_TIME function</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>CURRENT_TIMESTAMP</term>
<listitem>
<simpara>See CURRENT_TIMESTAMP function</simpara>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-SQL-NOTNULL-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
NOT NULL constraint
</TITLE>
<SYNOPSIS>
[ CONSTRAINT <replaceable class="parameter">name</replaceable> ] NOT NULL
</SYNOPSIS>
<PARA>
The NOT NULL constraint specifies a rule that a column may
contain only non-null values.
</PARA>
<PARA>
The NOT NULL constraint is a column constraint.
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">name</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional name of a constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
<REFSECT3 ID="R3-SQL-NOTNULL-1">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>ERROR: ExecAppend: Fail to add null value in not
null attribute "<replaceable class="parameter">column</replaceable>".</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
This error occurs at runtime if one tries to insert a null value
into a column which has a NOT NULL constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT3>
</REFSECT2>
<REFSECT2 ID="R2-SQL-UNIQUECLAUSE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
UNIQUE constraint
</TITLE>
<para>
Table Constraint definition
</para>
<synopsis>
[ CONSTRAINT <replaceable class="parameter">name</replaceable> ] UNIQUE ( <replaceable class="parameter">column</replaceable> [, ...] )
</SYNOPSIS>
<para>
Column Constraint definition
</para>
<synopsis>
[ CONSTRAINT <replaceable class="parameter">name</replaceable> ] UNIQUE
</SYNOPSIS>
<refsect3>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>
<replaceable class="parameter">name</replaceable>
</term>
<listitem>
<para>
An arbitrary name given to a constraint.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<replaceable class="parameter">column</replaceable>
</term>
<listitem>
<para>
A name of a column in a table.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect3>
<refsect3>
<title>Outputs</title>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
ERROR: Cannot insert a duplicate key into a unique index.
</term>
<listitem>
<para>
This error occurs at runtime if one tries to insert a
duplicate value into a column.
</para>
</listitem>
</varlistentry>
</variablelist></para>
</listitem>
</varlistentry>
</variablelist>
</refsect3>
<refsect3>
<title>Description</title>
<PARA>
The UNIQUE constraint specifies a rule that a group of one or
more distinct columns of a table may contain only unique values.
</para>
<para>
The column definitions of the specified columns do not have to
include a NOT NULL constraint to be included in a UNIQUE
constraint. Having more than one null value in a column without a
NOT NULL constraint, does not violate a UNIQUE constraint.
</PARA>
<PARA>
Each UNIQUE constraint must name a set of columns that is
different from the set of columns named by any other UNIQUE or
PRIMARY KEY constraint defined for the Table.
</PARA>
<Note>
<Para>
PostgreSQL automatically creates a unique index for each UNIQUE
constraint, to assure
data integrity. See CREATE INDEX for more information.
</Para>
</Note>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CONSTRAINT-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
CONSTRAINT clause
</TITLE>
<para>
Table constraint definition
</para>
<SYNOPSIS>
[ CONSTRAINT name ]
{ PRIMARY KEY constraint |
UNIQUE constraint |
CHECK constraint }
</SYNOPSIS>
<PARA>
Column constraint definition
</PARA>
<SYNOPSIS>
[ CONSTRAINT name ]
{ NOT NULL constraint |
PRIMARY KEY constraint |
UNIQUE constraint |
CHECK constraint }
</SYNOPSIS>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>
<replaceable class="parameter">name</replaceable>
</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
An arbitrary name given to an integrity constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>
<replaceable class="parameter">constraint</replaceable>
</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The definition of the constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
<para>
A Constraint is a named rule: a SQL object which helps define
valid sets of values by putting limits on the results of INSERT,
UPDATE or DELETE operations performed on a Base table.
</para>
<para>
There are two ways to define integrity constraints:
Table constraint and Column constraint.
</para>
<para>
A Table Constraint is an integrity Constraint defined on one or
more Columns of a Base table. The four variations of "Table
Constraint" are:
<simplelist columns="1">
<member>PRIMARY KEY</member>
<member>FOREIGN KEY</member>
<member>UNIQUE</member>
<member>CHECK</member>
</simplelist>
</para>
<para>
A column constraint is an integrity constraint defined as part
of a column definition, and logically becomes a table
constraint as soon as it is created. The column
constraints available are:
<simplelist columns="1">
<member>PRIMARY KEY</member>
<member>REFERENCES</member>
<member>UNIQUE</member>
<member>CHECK</member>
<member>NOT NULL</member>
</simplelist></para>
<note>
<para>
PostgreSQL does not yet (at release 6.3.2) support the FOREIGN KEY or
REFERENCES integrity constraints, although the parser will accept them.
Foreign keys may be partially emulated by triggers (See CREATE TRIGGER
statement)
</para>
</note>
<note>
<para>
PostgreSQL does not yet support either DOMAINs or ASSERTIONs.
</para>
</note>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CHECK-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<title>The CHECK constraint</title>
<SYNOPSIS>
[ CONSTRAINT name ] CHECK ( condition [, ...] )
</SYNOPSIS>
<refsect3 id="R3-SQL-CHECK-1">
<title>Inputs</title>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">name</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
An arbitrary name given to a constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>condition</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Any valid conditional expression.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</REFSECT3>
<REFSECT3 ID="R3-SQL-CHECK-2">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>
ERROR: ExecAppend: rejected due to CHECK constraint
"<replaceable class="parameter">table_column</replaceable>".
</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
This error occurs at runtime if one tries to insert an illegal
value into a column subject to a CHECK constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</REFSECT3>
<refsect3>
<title>Description</title>
<para>
The CHECK constraint specifies a rule that a group of one or
more columns of a table may contain only those values allowed by
the rule.
</para>
<PARA>
The CHECK constraint is either a table constraint or a column
constraint.
</PARA>
<PARA>
PostgreSQL automatically creates an unique index to assure
data integrity. (See CREATE INDEX statement)
</PARA>
<PARA>
The SQL92 CHECK column constraints can only be defined on, and
refer to, one column of the table. PostgreSQL does not have
this restriction.
</PARA>
</refsect3>
<refsect3>
<title>BUGS in CHECK constraint</title>
<PARA>
The following CHECK constraints gives a parse error like:
<programlisting>
ERROR: parser: parse error at or near "opname":
</programlisting>
<simplelist columns="1">
<member>CHECK ( <replaceable class="parameter">column</replaceable> BETWEEN 'A' AND 'Z' )</member>
<member>CHECK ( <replaceable class="parameter">column</replaceable> IN ('A','Z'))</member>
<member>CHECK ( <replaceable class="parameter">column</replaceable> NOT LIKE 'A%')</member>
</simplelist>
</para>
</refsect3>
</REFSECT2>
<REFSECT2 ID="R2-SQL-PRIMARYKEY-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
PRIMARY KEY clause
</TITLE>
<PARA>
Table constraint definition
</PARA>
<SYNOPSIS>
[ CONSTRAINT <REPLACEABLE CLASS="PARAMETER">name</REPLACEABLE> ] PRIMARY KEY ( <REPLACEABLE CLASS="PARAMETER">column</REPLACEABLE> [, ...] )
</SYNOPSIS>
<PARA>
Column constraint definition
</PARA>
<SYNOPSIS>
[ CONSTRAINT <REPLACEABLE CLASS="PARAMETER">name</REPLACEABLE> ] PRIMARY KEY
</SYNOPSIS>
<refsect3>
<title>Parameters</title>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><REPLACEABLE CLASS="PARAMETER">name</REPLACEABLE></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
An arbitrary name for the constraint.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><REPLACEABLE CLASS="PARAMETER">column</REPLACEABLE></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The name of a column in the table.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</para>
</refsect3>
<refsect3>
<title>Outputs</title>
<variablelist>
<varlistentry>
<term>ERROR: Cannot insert a duplicate key into a unique index.</term>
<listitem>
<para>
This occurs at run-time if one tries to insert a duplicate value into
a column subject to a PRIMARY KEY constraint.
</PARA>
</listitem>
</varlistentry>
</variablelist>
</refsect3>
<refsect3>
<title>Description</title>
<PARA>
The PRIMARY KEY constraint specifies a rule that a group of one
or more distinct columns of a table may contain only unique,
(not duplicates), non-null values. The column definitions of
the specified columns do not have to include a NOT NULL
constraint to be included in a PRIMARY KEY constraint.
</PARA>
<PARA>
A table's set of valid values may be constrained by only one
PRIMARY KEY constraint at a time.
</PARA>
<PARA>
The PRIMARY KEY constraint must name a set of columns that is
different from the set of columns named by any UNIQUE constraint
defined for the same table.
</PARA>
</REFSECT3>
<REFSECT3 ID="R3-SQL-PRIMARYKEY-3">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
Notes
</TITLE>
<PARA>
PostgreSQL automatically creates an unique index to assure
data integrity. (See CREATE INDEX statement)
</PARA>
</refsect3>
</REFSECT2>
</refsect1>
<REFSECT1 ID="R1-SQL-CREATETABLE-2">
<TITLE>
Usage
</TITLE>
<PARA>
Create table films and table distributors
</PARA>
<ProgramListing>
CREATE TABLE films (
code CHARACTER(5) CONSTRAINT firstkey PRIMARY KEY,
title CHARACTER VARYING(40) NOT NULL,
did DECIMAL(3) NOT NULL,
date_prod DATE,
kind CHAR(10),
len INTERVAL HOUR TO MINUTE
);
</ProgramListing>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(03) PRIMARY KEY DEFAULT NEXTVAL('serial'),
name VARCHAR(40) NOT NULL CHECK (name &lt;&gt; '')
);
</ProgramListing>
<PARA>
Create a table with a 2-dimensional array
</PARA>
<ProgramListing>
CREATE TABLE array (
vector INT[][]
);
</ProgramListing>
<PARA>
Define two NOT NULL column constraints on the table distributors
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(3) CONSTRAINT no_null NOT NULL,
name VARCHAR(40) NOT NULL
);
</ProgramListing>
<PARA>
Define a UNIQUE table constraint for the table films.
UNIQUE table constraints can be defined on one or more
columns of the table
</PARA>
<ProgramListing>
CREATE TABLE films (
code CHAR(5),
title VARCHAR(40),
did DECIMAL(03),
date_prod DATE,
kind CHAR(10),
len INTERVAL HOUR TO MINUTE,
CONSTRAINT production UNIQUE(date_prod)
);
</ProgramListing>
<PARA>
Defines a UNIQUE column constraint for the table distributors.
UNIQUE column constraints can only be defined on one column
of the table (the following two examples are equivalents).
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(03),
name VARCHAR(40) UNIQUE,
UNIQUE(name)
);
</ProgramListing>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(3),
name VARCHAR(40) UNIQUE
);
</ProgramListing>
<PARA>
Define a CHECK column constraint.
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(3) CHECK (did > 100),
name VARCHAR(40)
);
</ProgramListing>
<PARA>
Define a CHECK table constraint
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(3),
name VARCHAR(40)
CONSTRAINT con1 CHECK (did > 100 AND name > '')
);
</ProgramListing>
<PARA>
Define a PRIMARY KEY table constraint for the table films.
PRIMARY KEY table constraints can be defined on one or more
columns of the table
</PARA>
<ProgramListing>
CREATE TABLE films (
code CHAR(05),
title VARCHAR(40),
did DECIMAL(03),
date_prod DATE,
kind CHAR(10),
len INTERVAL HOUR TO MINUTE,
CONSTRAINT code_title PRIMARY KEY(code,title)
);
</ProgramListing>
<PARA>
Defines a PRIMARY KEY column constraint for table distributors.
PRIMARY KEY column constraints can only be defined on one column
of the table (the following two examples are equivalents)
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(03),
name CHAR VARYING(40),
PRIMARY KEY(did)
);
CREATE TABLE distributors (
did DECIMAL(03) PRIMARY KEY,
name VARCHAR(40)
);
</ProgramListing>
<para>
To assign a sequence as the default for the column did,
and a literal to the column name
</PARA>
<ProgramListing>
CREATE TABLE distributors (
did DECIMAL(3) DEFAULT NEXTVAL('serial'),
name VARCHAR(40) DEFAULT 'luso films'
);
</ProgramListing>
<REFSECT2 ID="R2-SQL-CREATETABLE-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<PARA>
CREATE TABLE/INHERITS is a PostgreSQL language extension.
</PARA>
</refsect2>
</REFSECT1>
<REFSECT1 ID="R1-SQL-CREATETABLE-3">
<TITLE>
Compatibility
</TITLE>
<PARA>
</PARA>
<REFSECT2 ID="R2-SQL-CREATETABLE-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<PARA>
In addition to normal CREATE TABLE, SQL92 also supports a
CREATE TEMPORARY TABLE statement.
</PARA>
<synopsis>
CREATE [ {GLOBAL | LOCAL} ] TEMPORARY TABLE table (
column type [DEFAULT value] [CONSTRAINT column_constraint] [, ...] )
[CONSTRAINT table_constraint ]
[ ON COMMIT {DELETE | PRESERVE} ROWS ]
</synopsis>
<para>
For temporary tables, the CREATE TEMPORARY TABLE statement
names a new table and defines the table's columns and
constraints.
</para>
<para>
The optional ON COMMIT clause of CREATE TEMPORARY TABLE
specifies whether or not the temporary table should be emptied of
rows whenever COMMIT is executed. If the ON COMMIT clause is
omitted, the default option, ON COMMIT DELETE ROWS, is assumed.
</para>
<para>
To create a temporary table:
</para>
<programlisting>
CREATE TEMPORARY TABLE actors (
id DECIMAL(03),
name VARCHAR(40),
CONSTRAINT actor_id CHECK (id &lt; 150)
) ON COMMIT DELETE ROWS
</programlisting>
<para>
TIP: In the current release of PostgreSQL (6.3.2), to create a temporary
table you must create and drop the table by explicit commands.
</para>
<REFSECT3 ID="R3-SQL-UNIQUECLAUSE-1">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
UNIQUE clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for UNIQUE:
Table Constraint definition
</PARA>
<synopsis>
[ CONSTRAINT name ]
UNIQUE ( column [, ...] )
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
Column Constraint definition
</para>
<synopsis>
[ CONSTRAINT name ]
UNIQUE
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
</refsect3>
<REFSECT3 ID="R3-SQL-NOTNULL-4">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
NOT NULL clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for NOT NULL:
</PARA>
<synopsis>
[ CONSTRAINT name ] NOT NULL
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
</REFSECT3>
<REFSECT3 ID="R3-SQL-DEFAULTCLAUSE-1">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
DEFAULT clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for the DEFAULT clause.
A DEFAULT clause is used to set the default value for a column
or a domain.
</para>
<synopsis>
DEFAULT <replaceable class="parameter">literal</replaceable> |
niladic USER function |
niladic datetime function |
NULL
</synopsis>
</refsect3>
<REFSECT3 ID="R3-SQL-CONSTRAINT-3">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
CONSTRAINT clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for CONSTRAINTs,
it also defines assertions and domain constraints.
</PARA>
<PARA>
An assertion is a special type of integrity constraint and share
the same namespace as other constraints.
However, an assertion is not necessarily dependent on one
particular base table as constraints are, so SQL-92 provides the
CREATE ASSERTION statement as an alternate method for defining a
constraint:
</para>
<synopsis>
CREATE ASSERTION name CHECK ( condition )
</synopsis>
<PARA>
Domain constraints are defined by CREATE DOMAIN or ALTER DOMAIN
statements:
</para>
<PARA>
Domain constraint:
</para>
<synopsis>
[ CONSTRAINT name ]
CHECK constraint
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
Table constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
{ PRIMARY KEY constraint |
FOREIGN KEY constraint |
UNIQUE constraint |
CHECK constraint }
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]</synopsis>
<para>
Column constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
{ NOT NULL constraint |
PRIMARY KEY constraint |
FOREIGN KEY constraint |
UNIQUE constraint |
CHECK constraint }
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
A CONSTRAINT definition may contain one deferment attribute
clause and/or one initial constraint mode clause, in any order.
<variablelist>
<varlistentry>
<term>NOT DEFERRABLE</term>
<listitem>
<para>
means that the Constraint must be checked for
violation of its rule after the execution of every SQL statement.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DEFERRABLE</term>
<listitem>
<para>
means that checking of the Constraint may be deferred
until some later time, but no later than the end of the current
transaction.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The constraint mode for every Constraint always has an initial
default value which is set for that Constraint at the beginning
of a transaction.
<variablelist>
<varlistentry>
<term>INITIALLY IMMEDIATE</term>
<listitem>
<para>
means that, as of the start of the transaction,
the Constraint must be checked for violation of its rule after the
execution of every SQL statement.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>INITIALLY DEFERRED</term>
<listitem>
<para>
means that, as of the start of the transaction,
checking of the Constraint may be deferred until some later time,
but no later than the end of the current transaction.</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect3>
<REFSECT3 ID="R3-SQL-CHECK-4">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
CHECK clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for CHECK:
</PARA>
<para>
A CHECK constraint is either a table constraint, a column
constraint or a domain constraint.
</para>
<para>
table constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
CHECK ( VALUE condition )
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
column constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
CHECK ( VALUE condition )
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
domain constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
CHECK ( VALUE condition )
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
CHECK domain constraints can be defined in either
a CREATE DOMAIN statement or an ALTER DOMAIN statement:
</para>
<programlisting>
CREATE DOMAIN duration AS SMALLINT
CONSTRAINT minutes CHECK (VALUE IN (90,120,180,240));
ALTER DOMAIN cities
ADD CONSTRAINT new_city CHECK (VALUE LIKE 'L%');
</programlisting>
</refsect3>
<REFSECT3 ID="R3-SQL-PRIMARYKEY-1">
<REFSECT3INFO>
<DATE>1998-04-15</DATE>
</REFSECT3INFO>
<TITLE>
PRIMARY KEY clause
</TITLE>
<PARA>
SQL92 specifies some additional capabilities for PRIMARY KEY:
</para>
<PARA>
Table Constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
PRIMARY KEY ( column [, ...] )
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
<para>
Column Constraint definition:
</para>
<synopsis>
[ CONSTRAINT name ]
PRIMARY KEY
[ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ]
[ [ NOT ] DEFERRABLE ]
</synopsis>
</refsect3>
</refsect2>
</refsect1>
</refentry>
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