Two Ways To Compute Factorial

In PostgreSQL, there are two ways to compute the factorial of a number. There is a prefix operator and a postfix operator. The prefix operator is !! and can be used like so:

> select !!5;
 ?column?
----------
      120

The postfix operator is ! and can be used like so:

> select 5!;
 ?column?
----------
      120

See the mathematical functions and operators docs for more details.