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mysql中乘法的函数的使用方法

MySQL 聚合函数里面提供了加,平均数。最小,最大等,可是没有提供乘法,我们这里来利用MYSQL现有的GROUP_CONCAT函数实现聚合乘法。

先创建一张演示样例表:CREATE TABLE `tb_seq` (

`num` int(10) NOT NULL,

`seq_type` enum('yellow','green','red') NOT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

插入演示样例数据:

insert into `tb_seq`(`num`,`seq_type`)

values (4,'green'),(1,'red'),(3,'green'),

(1,'red'),(8,'red'),(4,'yellow'),

(8,'red'),(7,'yellow'),(10,'red'),

(1,'red'),(1,'red'),(1,'yellow'),

(5,'green'),(9,'red'),(1,'yellow'),

(6,'yellow');

创建基于逗号分隔符的字符串乘法,前提是字符串逗号分隔的都是数字。

DELIMITER $$

USE `t_girl`$$

DROP FUNCTION IF EXISTS `func_multiple`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `func_multiple`(

f_nums VARCHAR(1000)

) RETURNS DOUBLE(10,2)

BEGIN

-- Created by ytt 2014/10/21.

DECLARE result DOUBLE(10,2) DEFAULT 1;

DECLARE cnt,i INT DEFAULT 0;

SET cnt = CHAR_LENGTH(f_nums) - CHAR_LENGTH(REPLACE(f_nums,',','')) + 1;

WHILE i < cnt

DO

-- get multiple result.

SET result = result * REVERSE(SUBSTRING_INDEX(REVERSE(SUBSTRING_INDEX(f_nums,',',i+1)),',',1));

SET i = i + 1;

END WHILE;

SET result = ROUND(result,2);

RETURN result;

END$$

DELIMITER ;

好了。我们利用我创建的函数以及MYSQL自带的GROUP_CONCAT聚合函数就能够非常方便的实现乘法了。

SELECT seq_type,func_multiple(GROUP_CONCAT(num ORDER BY num ASC SEPARATOR ',')) AS multiple_num FROM tb_seq WHERE 1 GROUP BY seq_type;

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

| seq_type | multiple_num |

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

| yellow | 168.00 |

| green | 60.00 |

| red | 5760.00 |

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

3 rows in set (0.00 sec)

本文标签: mysql中乘法的函数的使用方法