# 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:

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

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

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

See the [mathematical functions and operators docs](http://www.postgresql.org/docs/8.1/static/functions-math.html) for more details.


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