<< SELECT | FB 2.0 Language Reference | Transaction control statements >>

UPDATE

Available in: DSQL, ESQL, PSQL

Description

Changes values in a table (or in one or more tables underlying a view). The columns affected are specified in the SET clause; the rows affected may be limited by the WHERE and ROWS clauses.

Syntax

 UPDATE [TRANSACTION name] {tablename | viewname} [[AS] alias]
    SET col = newval [, col = newval ...]
    [WHERE {search-conditions | CURRENT OF cursorname}]
    [PLAN plan_items]
    [ORDER BY sort_items]
    [ROWS <m> [TO <n>]]

 <m>, <n> ::= Any expression evaluating to an integer.

Restrictions

  • The TRANSACTION directive is only available in ESQL.
  • In a pure DSQL session, WHERE CURRENT OF isn't of much use, since there exists no DSQL statement to create a cursor.
  • The PLAN, ORDER BY and ROWS clauses are not available in ESQL.
  • New in 2.0: No column may be SET more than once in the same UPDATE statement.

back to top of page

COLLATE subclause for text BLOB columns

Added in: 2.0

Description

COLLATE subclauses are now also supported for text BLOBs.

Example

 update MyTable
   set NameBlobSp = 'Juan'
   where NameBlobBr collate pt_br = 'Joćo'

back to top of page

ORDER BY

Available in: DSQL, PSQL

Added in: 2.0

Description

UPDATE now allows an ORDER BY clause. This only makes sense in combination with ROWS, but is also valid without it.

PLAN

Available in: DSQL, PSQL

Added in: 2.0

Description

UPDATE now allows a PLAN clause, so users can optimize the operation manually.

back to top of page

Relation alias makes real name unavailable

Changed in: 2.0

Description

If you give a table or view an alias in a Firebird 2.0 or above statement, you must use the alias, not the table name, if you want to qualify fields from that relation.

Examples

Correct usage:

 update Fruit set sort = 'pisang' where ...

 update Fruit set Fruit.sort = 'pisang' where ...

 update Fruit F set sort = 'pisang' where ...

 update Fruit F set F.sort = 'pisang' where ...

No longer possible:

 update Fruit F set Fruit.sort = 'pisang' where ...

back to top of page

ROWS

Available in: DSQL, PSQL

Added in: 2.0

Description

Limits the amount of rows updated to a specified number or range.

Syntax

 ROWS <m> [TO <n>]

 <m>, <n> ::= Any expression evaluating to an integer.

With a single argument m, the update is limited to the first m rows of the dataset defined by the table or view and the optional WHERE and ORDER BY clauses.

Points to note:

  • If m > the total number of rows in the dataset, the entire set is updated.
  • If m = 0, no rows are updated.
  • If m < 0, an error is raised.

With two arguments m and n, the update is limited to rows m to n inclusively. Row numbers are 1-based.

Points to note when using two arguments:

  • If m > the total number of rows in the dataset, no rows are updated.
  • If m lies within the set but n doesn't, the rows from m to the end of the set are updated.
  • If m < 1 or n < 1, an error is raised.
  • If n = m-1, no rows are updated.
  • If n < m-1, an error is raised.

ROWS can also be used with the SELECT and DELETE statements.

See also:
UPDATE
DELETE
GRANT
INSERT
REVOKE
SELECT

back to top of page
<< SELECT | FB 2.0 Language Reference | Transaction control statements >>