Reserved words are part of the Firebird SQL language. They cannot be used as identifiers (e.g. table or procedure names), except when enclosed in double quotes in Dialect 3. However, you should avoid this unless you have a compelling reason.

Keywords are also part of the language. They have a special meaning when used in the proper context, but they are not reserved for Firebird's own and exclusive use. You can use them as identifiers without double-quoting.

The following reserved words have been added to Firebird:

• BIGINT
• BIT_LENGTH
• BOTH
• CASE
• CHAR_LENGTH
• CHARACTER_LENGTH
• CLOSE
• CROSS
• CURRENT_CONNECTION
• CURRENT_ROLE
• CURRENT_TRANSACTION
• CURRENT_USER
• FETCH
• LEADING
• LOWER
• OCTET_LENGTH
• OPEN
• RECREATE
• RELEASE
• ROW_COUNT
• ROWS
• SAVEPOINT
• TRAILING
• TRIM
• USING

The following words have been added to Firebird as non-reserved keywords:

• BACKUP
• BLOCK
• COALESCE
• COLLATION
• COMMENT
• DELETING
• DIFFERENCE
• IIF
• INSERTING
• LAST
• LEAVE
• LOCK
• NEXT
• NULLIF
• NULLS
• RESTART
• RETURNING
• SCALAR_ARRAY
• SEQUENCE
• STATEMENT
• UPDATING

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The following words are no longer reserved in Firebird 2.0, but are still recognized as keywords:

• ACTION
• CASCADE
• FREE_IT
• RESTRICT
• ROLE
• TYPE
• WEEKDAY
• YEARDAY

The following are no longer keywords in Firebird 2.0:

• BASENAME
• CACHE
• CHECK_POINT_LEN
• GROUP_COMMIT_WAIT
• LOG_BUF_SIZE
• LOGFILE
• NUM_LOG_BUFS
• RAW_PARTITIONS

The following words are not reserved in Firebird 2.0, but should be avoided as identifiers because they will likely be reserved in future versions:

• ABS
• BOOLEAN
• FALSE
• TRUE
• UNKNOWN