A CASE expression is a PROC SQL feature that can be used to evaluate whether a particular condition has been met (see section 4.3).

A CASE expression can be used to process a table’s rows (see section 4.3).

A single value is returned from its evaluation of each row in a table (or view) (see section 4.3).

Logic conditions can be combined using the logical operators AND and OR (see section 4.3.3).

A missing or null value is returned when an ELSE expression is not specified and each when-condition is “false” (see section 4.3.3).

A missing value is not the same as a value of 0 (zero) or as a blank character since it represents a unique value or a lack of a value (see section 4.3.3).

PROC SQL can be used with the SAS macro facility to perform common and repetitive tasks (see section 4.4).

Simple, but effective, user-defined macros combined with the SQL procedure can be created for all users (see section 4.4.2).

Identify duplicate rows in a table by creating a user-defined macro (see section 4.4.2.4).