CursorsIn-place updates 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
.
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.
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.
SELECT RECEIVED, SOURCE, SUBJECT, NOTE_TEXT FROM SAMP.IN_TRAY FOR UPDATE
For information about how indexes affect performance, see
.