Difference between revisions of "DELETE"

Revision as of 09:47, 30 November 2009

Purpose

Mark records in the active table for deletion

Syntax

DELETE [<scope>]

[FOR <condition>]

[WHILE <condition>]

See Also

ERASE, LOCATE, PACK, RECALL, SEEK, SET COMPATIBLE, SET DELETED, SET FILTER, USE, ZAP

Description

The DELETE command marks records in the active table for deletion. The default <scope> deletes the current record. If the FOR clause is specified, the default scope is ALL. If the WHILE clause is specified, the default scope is REST.

If SET FILTER TO <condition> is in effect, then only those records that satisfy the filter are deleted. If a record is already marked for deletion then the <scope> will be extended. Any records which have been marked for deletion with the DELETE command can be reinstated using the RECALL command.

Records that are marked for deletion are only physically removed from the table after the PACK command has been issued. If the table is indexed, then the Recital/4GL will process the records in the table in the order of the master index file. If the active table is shareable, then the Recital/4GL will automatically lock each record in turn, mark it for deletion if required, then unlock the record.

At the end of a DELETE operation with a FOR or WHILE condition, the record pointer is positioned to EOF() if SET COMPATIBLE TO <XBASE> is in effect.

FOR <condition>

If the FOR clause is specified, then only those records which satisfy the <condition> are deleted. If FOR and WHILE clauses are used at the same time, the default <scope> is ALL.

WHILE <condition>

The WHILE clause can be used to restrict the number of records checked against a particular FOR <condition>, therefore optimizing the deletion process.

Example

use patrons index names, events
delete all for event = "HAMLET"
 
use patrons index events, names
seek "OPERA"
delete rest;
  for date < date();
  while event = "OPERA"

Products

Recital Server, Recital