SAS - Efficiency

Some SAS recommendations for making the code more efficient.

• Avoid necessary DATA steps.
• IF statements before loading raw data.
• Use of WHERE statements in procedures.
• Drop unnecessary variables by using KEEP/DROP.
• Optimize size of variables using LENGTH.
• Use of IF-THEN-ELSE statements when possible instead of an IF-THEN sequence.
• Order of conditions inside the statements. The most frequent case should be the first.
  
• Multiple OR operators instead of IN.
• Use of DATA _NULL_ when creating Reports.
• Use of permanent data sets in libraries.
• use of PROC DATASETS to modify variables, instead of DATA statements.
• PROC APPEND to join similar datasets.
• Use RETAIN statement to initialize contents
• Avoid unnecessary sorts: two-level sort instead of one-level sort and a two-level sort.
• Sort only what we have to sort
• Sort: Using NOEQUALS if we do not neet the relative order.