SELECT FOR UPDATE Statement 

The SELECT … FOR UPDATE statement retrieves columns from a uniquely specified row of database table and simultaneously set an update lock on the selected row. This statement is specific to Open SQL.

In Open SQL / SQLJ and Open SQL /JDBC, the update lock is set on the row after execution of the statement.

Syntax

<select for update statement> ::=     SELECT ( ALL )? <select list>                  FROM <table reference> <where clause>                  FOR UPDATE ( OF <column reference list> )? <column reference list> ::= <column reference> ( ',' <column reference> )*.

Some semantic restrictions apply:

·        the FROM clause can contain only a single table

·        for all primary key columns of the table, the WHERE clause must contain <comparison predicate> with the comparison operator '='; all these comparison predicates must be combined by AND

·        the SELECT list must not contain set functions

Example

SELECT employee_name FROM employees WHERE employee_id = 123 FOR UPDATE

Example 1: The SELECT FOR UPDATE Statement. From the table employees a single row with the key value employee_id = 123 is selected. Simultaneously, an update lock is set on the selected row.

See

Select List, Table Reference, WHERE Clause, Column Reference