Information is now in the chapter on syntax in the User's Guide.

src/tools/SQL_keywords

-These are the standard SQL'92 keywords:
-absolute
-action
-add
-all
-allocate
-alter
-and
-any
-are
-as
-asc
-assertion
-at
-authorization
-avg
-begin
-between
-bit
-bit_length
-both
-by
-cascade
-cascaded
-case
-cast
-catalog
-char
-character
-char_length
-character_length
-check
-close
-coalesce
-collate
-collation
-column
-commit
-connect
-connection
-constraint
-constraints
-continue
-convert
-corresponding
-count
-create
-cross
-current
-current_date
-current_time
-current_timestamp
-current_user
-cursor
-date
-day
-deallocate
-dec
-decimal
-declare
-default
-deferrable
-deferred
-delete
-desc
-describe
-descriptor
-diagnostics
-disconnect
-distinct
-domain
-double
-drop
-else
-end
-end-exec
-escape
-except
-exception
-exec
-execute
-exists
-external
-extract
-false
-fetch
-first
-float
-for
-foreign
-found
-from
-full
-get
-global
-go
-goto
-grant
-group
-having
-hour
-identity
-immediate
-in
-indicator
-initially
-inner
-input
-insensititve
-insert
-int
-integer
-intersect
-interval
-into
-is
-isolation
-join
-key
-language
-last
-leading
-left
-level
-like
-local
-lower
-match
-max
-min
-minute
-module
-month
-names
-national
-natural
-nchar
-next
-no
-not
-null
-nullif
-numeric
-octet_length
-of
-on
-only
-open
-option
-or
-ordered
-outer
-output
-overlaps
-partial
-postion
-precision
-prepare
-preserve
-primary
-prior
-privledges
-procedure
-public
-read
-real
-references
-relative
-restrict
-revoke
-right
-rollback
-rows
-schema
-scroll
-second
-section
-select
-session
-session_user
-set
-size
-smallint
-some
-sql
-sqlcode
-sqlerror
-sqlstate
-substring
-sum
-system_user
-table
-temporary
-then
-time
-timestamp
-timezone_hour
-timezone_minute
-to
-trailing
-transaction
-translate
-translation
-trim
-true
-union
-unique
-unknown
-update
-upper
-usage
-user
-using
-value
-values
-varchar
-varying
-view
-when
-whenever
-where
-with
-work
-write
-year
-zone