mysql自定义函数怎么写？

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)

DELIMITER $$

CREATE FUNCTION `ChkInsert`(in_pk int) returns int

begin

declare _count int

declare _returnValue int

set _count = 0

select count(列1) into _count from 你的表 where 列1 = in_pk

if _count >0 then

set _returnValue = 2

else

insert into 你的表 ( 列1 ) values ( in_pk )

set _returnValue = 0

end if

return _returnValue

end $$

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