mysql> select * from test;
+-------+
| money |
+-------+
|     1 |
|     2 |
|     3 |
+-------+
3 rows in set (0.00 sec)

mysql> select stddev(money) from test;
+---------------+
| stddev(money) |
+---------------+
|        0.8165 |
+---------------+
1 row in set (0.00 sec)