SELECT IF expression.
SELECT IF selects cases for analysis based on the value of a boolean expression. Cases not selected are permanently eliminated from the active file, unless TEMPORARY is in effect (see TEMPORARY).
Specify a boolean expression (see Expressions). If the value of the expression is true for a particular case, the case will be analyzed. If the expression has a false or missing value, then the case will be deleted from the data stream.
Place SELECT IF as early in the command file as possible. Cases that are deleted early can be processed more efficiently in time and space.
When SELECT IF is specified following TEMPORARY (see TEMPORARY), the LAG function may not be used (see LAG).