MySql创建函数

首先需要查看一下创建函数的功能是否开启：
X:\proper\mysql\bin>mysql -h localhost -u root -p
Enter password: **********
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12 to server version: 5.0.22-community-nt-log
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> show variables like '%func%';
+-----------------------------------------+-------+
| Variable_name                            | Value |
+-----------------------------------------+-------+
| log_bin_trust_function_creators | ON    |
+-----------------------------------------+-------+
1 row in set (0.02 sec)
如果Value处值为OFF，则需将其开启。
mysql> set global log_bin_trust_function_creators=1;
创建函数时，先选择数据库，
mysql> use xxx;
Database changed
delimiter $$是设置 $$为命令终止符号，代替分号，因为分号在begin...end中会用到；
mysql> delimiter $$
mysql> create function test(t varchar(255))
    -> returns varchar(255)
    -> begin
    -> return left(t,1);
    -> end
    -> $$
Query OK, 0 rows affected (0.13 sec)
函数创建成功后需恢复分号为命令终止符号。
mysql> delimiter ;
测试：
mysql> select test('alpha');
+----------------+
| test('alpha') |
+---------------+
| a                 |
+---------------+
1 row in set (0.02 sec)
删除函数：
mysql> drop function test;
Query OK, 0 rows affected (0.11 sec)