FOR UPDATE clause

The FOR UPDATE clause is an optional part of a SELECT statement. Cursors are read-only by default. The FOR UPDATE clause specifies that the cursor should be updatable, and enforces a check during compilation that the SELECT statement meets the requirements for an updatable cursor. For more information about updatability, see Requirements for Updatable Cursors.

Syntax

FOR
{
    READ ONLY | FETCH ONLY |
    UPDATE [ OF Simple-column-Name [ , Simple-column-Name]* ]
}

Simple-column-Name refers to the names visible for the table specified in the FROM clause of the underlying query.

Note: The use of the FOR UPDATE clause is not mandatory to obtain an updatable JDBC ResultSet. As long as the statement used to generate the JDBC ResultSet meets the requirements for updatable cursor, it is sufficient for the JDBC Statement that generates the JDBC ResultSet to have concurrency mode ResultSet.CONCUR_UPDATABLE for the ResultSet to be updatable.

The optimizer is able to use an index even if the column in the index is being updated. For more information about how indexes affect cursors, see Tuning Derby.

SELECT RECEIVED, SOURCE, SUBJECT, NOTE_TEXT FROM SAMP.IN_TRAY FOR UPDATE
Related concepts
Interaction with the dependency system
CREATE statements
DROP Statements
RENAME statements
SET statements
Related reference
ALTER TABLE statement
GRANT statement
REVOKE statement
CALL (PROCEDURE)
CONSTRAINT clause
DECLARE GLOBAL TEMPORARY TABLE statement
DELETE statement
FROM clause
GROUP BY clause
HAVING clause
INNER JOIN
INSERT statement
JOIN operation
LEFT OUTER JOIN
LOCK TABLE statement
ORDER BY clause
Query
RIGHT OUTER JOIN
ScalarSubquery
SelectExpression
SELECT statement
TableExpression
TableSubquery
UPDATE statement
VALUES expression
WHERE clause
WHERE CURRENT OF clause