11-28-2011 09:54 AM
Only differnce is when it is applied.
If you use the KEEP= option on an input dataset then only those variables are loaded into the data step (or proc step) whereas when it is on the output dataset or the KEEP statement is used all of the variables are available during the step.
Another place where which makes a difference is when using RENAME statement. The second datastep below will generate an error.
data one ;
keep name age;
data two (keep=name age);
11-28-2011 10:17 AM
And, to add to Tom's comments, when used as an option in a data or set statement, the drop, keep and rename statements are applied in alphabetical order (i.e., first drop, then keep, then rename). Thus, using Tom's example,
set sashelp.class (keep=name age rename=(age=age2));
would work as the rename wouldn't take effect until AFTER the keep statement.