17.10 - Usage Notes - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - SQL Functions, Expressions, and Predicates

Advanced SQL Engine
Teradata Database
Release Number
Release Date
July 2021
Content Type
Programming Reference
Publication ID
English (United States)

A scalar_expression_n in the argument list may be evaluated twice: once as a search condition and again as a return value for that search condition.

Using a nondeterministic function, such as RANDOM, in a scalar_expression_n may have unexpected results, because if the first calculation of scalar_expression_n is not NULL, the second calculation of that scalar_expression_n, which is returned as the value of the COALESCE expression, might be NULL.

You can use a scalar subquery in a COALESCE expression. However, if you use a non-scalar subquery (a subquery that returns more than one row), a runtime error is returned.