DELETE

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DELETE

COLLATE subclause for
text BLOB columns]
ORDER BY
PLAN
Relation alias makes
real name unavailable
ROWS

`DELETE`

Available in: DSQL, ESQL, PSQL

Description

Deletes rows from a database table (or from one or more tables underlying a view), depending on the WHERE and ROWS clauses.

Syntax

 DELETE
    [TRANSACTION name]
    FROM {tablename | viewname} [[AS] alias]
    [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.

`COLLATE` subclause for text BLOB columns

Added in: 2.0

Description

COLLATE subclauses are now also supported for text BLOBs.

Example

 delete from MyTable
   where NameBlob collate pt_br = 'João'

`ORDER BY`

Available in: DSQL, ESQL

Added in: 2.0

Description

DELETE 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

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

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:

 delete from Cities where name starting 'Alex'

 delete from Cities where Cities.name starting 'Alex'

 delete from Cities C where name starting 'Alex'

 delete from Cities C where C.name starting 'Alex'

No longer possible:

 delete from Cities C where Cities.name starting 'Alex'

`ROWS`

Available in: DSQL, PSQL

Added in: 2.0

Description

Limits the amount of rows deleted 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 deletion 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 deleted.
If m = 0, no rows are deleted.
If m < 0, an error is raised.

With two arguments m and n, the deletion 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 deleted.
If m lies within the set but n doesn't, the rows from m to the end of the set are deleted.
If m < 1 or n < 1, an error is raised.
If n = m-1, no rows are deleted.
If n < m-1, an error is raised.

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