MySQL自定义函数简单用法示例

DELIMITER $$
DROP FUNCTION IF EXISTS `sp_test`.`getdate`$$
CREATE FUNCTION `sp_test`.`getdate`(gdate datetime) RETURNS varchar(255)
BEGIN
DECLARE x VARCHAR(255) DEFAULT '';
SET x= date_format(gdate,'%Y年%m月%d日%h时%i分%s秒');
RETURN x;
END $$
DELIMITER ;

SELECT getdate('2009-06-23 000000');

DELIMITER $$
DROP FUNCTION IF EXISTS `sp_test`.`cutString` $$
CREATE FUNCTION `sp_test`.`cutString`(s VARCHAR(255),n INT) RETURNS varchar(255)
BEGIN
IF(ISNULL(s)) THEN RETURN '';
ELSEIF CHAR_LENGTH(s)<n THEN RETURN s;
ELSEIF CHAR_LENGTH(S)=n THEN RETURN '相等';
ELSE RETURN CONCAT(LEFT(s,n),'...');
END IF;
END $$
DELIMITER ;

SELECT cutString('abcdefghijklmnopqrstuvwxyz',5);

DELIMITER $$
DROP FUNCTION IF EXISTS `sp_test`.`morestar`$$
CREATE FUNCTION `sp_test`.`morestar`(n INT) RETURNS text
BEGIN
DECLARE i INT DEFAULT 0;
DECLARE s TEXT DEFAULT '';
myloop:LOOP
SET i=i+1;
SET s = CONCAT(s,'');
IF i > n THEN LEAVE myloop;
END IF;
END LOOP myloop;
RETURN s;
END $$
DELIMITER ;

SELECT morestar(5);