The rules regarding the use of the COMPUTE and COMPUTE BY clauses are listed below:

1>The DISTINCT keyword cannot be used with the aggregate functions.

2>All columns referred to in the COMPUTE clause must appear in the SELECT column list.

3>The ORDER BY clause must be used whenever the COMPUTE BY clause is used.

4>The ORDER BY clause can be eliminated only when the COMPUTE clause is used.

5>The columns listed in the COMPUTE BY clause must match the columns used in the ORDER BY clause.

6>More than one COMPUTE clause can be used in the SELECT statement to produce a result with subtotals and a grand total.

7>The different aggregate functions can be used on more than one column with the COMPUTE BY clause.