COALESCE « Data Convert Functions « SQL Server / T-SQL Tutorial

13.2.1.COALESCE is equivalent to a CASE expression that returns the first NOT NULL expression in a list of expressions.
13.2.2.Returning the First Non NULL Value in a List of Expressions
13.2.3.COALESCE() saves quite a lot of IF or CASE decision logic.
13.2.4.A SELECT statement that uses the COALESCE function
13.2.5.A SELECT statement that substitutes a different data type