Teradata COALESCE Function: Purpose, Syntax, Alternative and Data Types

COALESCE receives a list of scalars as arguments and returns the first value that is not NULL. If all scalars are NULL, then COALESCE returns NULL.

SELECT COALESCE(skalar1, skalar2, skalar3,…,skalarN) FROM Customer;

The COALESCE function is a simplified option for the following CASE statement:

SELECT
CASE
WHEN skalar1 IS NOT NULL THEN skalar1
WHEN skalar2 IS NOT NULL THEN skalar2
..
WHEN skalarN IS NOT NULL THEN skalarN
ELSE NULL
END
FROM Customer;

BLOB scalars must be cast to BYTE or VARBYTE.
Scalars of the type CLOB must be cast to CHAR or VARCHAR.
Several UDT scalars must all be of the same type.

Yes, it is ANSI SQL:2011 compliant.