Example: UPDATE With a Correlated Subquery in its WHERE Clause - Analytics Database - Teradata Vantage

SQL Data Manipulation Language

Deployment
VantageCloud
VantageCore
Edition
Enterprise
IntelliFlex
VMware
Product
Analytics Database
Teradata Vantage
Release Number
17.20
Published
June 2022
Language
English (United States)
Last Update
2024-04-05
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lifecycle
latest
Product Category
Teradata Vantage™

For a noncorrelated subquery, change the subquery to include all tables it references 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.