17.05 - Rules for Using Scalar Subqueries in UPDATE Requests - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Manipulation Language

Advanced SQL Engine
Teradata Database
Release Number
Release Date
January 2021
Content Type
Programming Reference
Publication ID
English (United States)
The following rules apply to using scalar subqueries in UPDATE requests:
  • You can specify scalar subqueries in the FROM and WHERE clauses of an UPDATE request in the same way as you would for a SELECT request. See Scalar Subqueries. You can only specify a scalar subquery in the FROM clause of an UPDATE request as an expression within a derived table. You cannot, however, code a derived table as a scalar subquery.
  • You can specify scalar subqueries in the SET clause of an UPDATE request.
  • When you specify a correlated scalar subquery in the SET clause, even if the request has no FROM clause, the database treats the update as a joined update. See Example: UPDATE With a Noncorrelated Subquery in its WHERE Clause.
  • You can specify an UPDATE statement with scalar subqueries in the body of a trigger.

    However, the database processes any noncorrelated scalar subqueries specified in the FROM, WHERE, or SET clauses of an UPDATE statement in a row trigger as a single-column single-row spool instead of as a parameterized value.