is generally a sequence of operands and operators that form a set of instructions that are performed to produce a resulting value. You use expressions in SAS program statements to create variables, assign values, calculate new values, transform variables, and perform conditional processing. SAS expressions can resolve to numeric values, character values, or Boolean values.
is a type of SAS expression that is used within a WHERE statement or WHERE= data set option to specify a condition for selecting observations for processing in a DATA or PROC step. For syntax and further information on WHERE expressions, see WHERE-Expression Processing and SAS Language Reference: Dictionary