mysql存储过程和函数怎么写

1、函数必须指定返回值，且参数默认为IN类型。

2、存储过程没返回值，参数可以是 IN,OUT,IN OUT类型，有的人可能会理解成OUT 也算是返回值。

3、调用方式：函数 select my_fun() 过程 call my_pro( )

4、DEMO

mysql>call my_pro(1,2,@c)

Query OK, 0 rows affected (0.00 sec)

mysql>select @c

+------+

| @c |

+------+

|3 |

+------+

1 row in set (0.00 sec)

mysql>select my_fun(1,2)

+-------------+

| my_fun(1,2) |

+-------------+

| 3 |

+-------------+

1 row in set (0.00 sec)

mysql>CREATE FUNCTION HelloWorld4()

->RETURNS VARCHAR(20)

->BEGIN

->  RETURN 'Hello World!'

->END

->//

Query OK, 0 rows affected (0.00 sec)

mysql>select HelloWorld4() //

+---------------+

| HelloWorld4() |

+---------------+

| Hello World!  |

+---------------+

1 row in set (0.00 sec) ...展开mysql>CREATE FUNCTION HelloWorld4()

->RETURNS VARCHAR(20)

->BEGIN

->  RETURN 'Hello World!'

->END

->//

Query OK, 0 rows affected (0.00 sec)

mysql>select HelloWorld4() //

+---------------+

| HelloWorld4() |

+---------------+

| Hello World!  |

+---------------+

1 row in set (0.00 sec)

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