> For the complete documentation index, see [llms.txt](https://ploegert.gitbook.io/til/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ploegert.gitbook.io/til/programmy/linux/is-app-installed/math-operations/two-ways-to-compute-factorial.md).

# 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.