16.20 - Usage Notes - Teradata Database

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

prodname
Advanced SQL Engine
Teradata Database
vrm_release
16.20
created_date
March 2019
category
Programming Reference
featnum
B035-1145-162K

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.