Use the SHOW CREATE FUNCTION command : Function Data Dictionary « Procedure Function « MySQL Tutorial

1. MySQL Tutorial
2. Procedure Function
3. Function Data Dictionary

mysql>
mysql>
mysql> DELIMITER //
mysql>
mysql> CREATE FUNCTION myFunction (item_sum DECIMAL(10,2))
    -> RETURNS DECIMAL(10,1)
    -> BEGIN
    ->
    ->
    -> RETURN ROUND(item_sum,1);
    ->
    -> END
    -> //
Query OK, 0 rows affected (0.02 sec)

mysql> DELIMITER ;
mysql>
mysql> select myFunction(123.12);
+--------------------+
| myFunction(123.12) |
+--------------------+
|              123.1 |
+--------------------+
1 row in set (0.00 sec)

mysql>
mysql>
mysql>
mysql> SHOW CREATE FUNCTION test.myFunction\G
*************************** 1. row ***************************
       Function: myFunction
       sql_mode:
Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `myFunction`(item_sum DECIMAL(10,2)) RETURNS decimal(10,1)
BEGIN
RETURN ROUND(item_sum,1);
END
1 row in set (0.00 sec)

mysql>
mysql> drop function myFunction;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>