[!INCLUDE [sql-asdb-asdbmi-asa-pdw-fabricse-fabricdw](../../includes/applies-to-version/sql-asdb-asdbmi-asa-pdw-fabricse-fabricdw.md)] Returns a null value if the two ...

NULLIF(expr1, expr2) returns NULL if the two expressions are equal or else returns expr1. It's a function used by many DBs like PostgreSQL, MySQL, MS-SQL server and others.