Example: UPDATE with a Correlated Subquery in the WHERE Clause - Teradata VantageCloud Lake

For a noncorrelated subquery, change the subquery to include all referenced tables in the inner FROM clause.

     UPDATE publisher
     SET pubnum = NULL
     WHERE 0 = (SELECT COUNT(*)
                FROM book, publisher
                WHERE book.pubnum = publisher.pubnum);

The request does not contain a correlated subquery and the condition in the subquery has a local defining reference. The count, determined once, is nonzero, and no rows are deleted.

For additional examples of correlated and noncorrelated subqueries, see Correlated Subqueries.