case expression simplifies many conditional Transact-SQL constructs. Instead of using a series of if statements, case expression allows you to use a series of conditions that return the appropriate values when the conditions are met. case expression is ANSI SQL92 compliant.
With case expression, you can:
Simplify queries and write more efficient code
Convert data between the formats used in the database (such as int) and the format used in an application (such as char)
Return the first non-null value in a list of columns
Compare two values and return the first value if the values do not match, or a NULL value if the values do match
Write queries that avoid division by 0
case expression includes the keywords case, when, then, coalesce, and nullif. coalesce and nullif are an abbreviated form of case expression. For details on case expression syntax, see the Reference Manual.
