03-08-2018 03:38 AM - edited 03-08-2018 03:45 AM
Using WHERE ALSO allows you to apply multiple WHERE statements to a SAS procedure or DATA step simultaneously. The usual behaviour of using multiple WHERE statements is that the last one overwrites any previous ones. WHERE ALSO changes that behaviour to make ALL WHERE statements be used. For example:
proc sort data = sashelp.class out = class; by age; where sex = 'F'; where also age > 14;
* Same result as single statement: where sex = 'F' and age > 14; run;
The effect of the two WHERE statements is to select all females aged over 14.
03-08-2018 04:40 AM
The simplest answer here is that in 16+ of SAS programming I have never seen where also used, nor even come across it until you posted this question. Logical operators and brackets are the ones used most.