Cursor (databases) - Positioned Update/delete Statements

Positioned Update/delete Statements

Cursors can not only be used to fetch data from the DBMS into an application but also to identify a row in a table to be updated or deleted. The SQL:2003 standard defines positioned update and positioned delete SQL statements for that purpose. Such statements do not use a regular WHERE clause with predicates. Instead, a cursor identifies the row. The cursor must be opened and already positioned on a row by means of FETCH statement.

UPDATE table_name SET ... WHERE CURRENT OF cursor_name DELETE FROM table_name WHERE CURRENT OF cursor_name

The cursor must operate on an updatable result set in order to successfully execute a positioned update or delete statement. Otherwise, the DBMS would not know how to apply the data changes to the underlying tables referred to in the cursor.

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