[mysql] custom split function

Customize the split function to achieve the purpose of splitting a character string into an array.

1. Create function code:

DELIMITER $$

DROP FUNCTION IF EXISTS `split`$$

CREATE FUNCTION `split`(str VARCHAR(4000), delimiter VARCHAR(12), pos INT)
RETURNS VARCHAR(2000)
BEGIN
    DECLARE ret VARCHAR(2000);

    SET ret = REPLACE(SUBSTRING(SUBSTRING_INDEX(str, delimiter, pos),
               LENGTH(SUBSTRING_INDEX(str, delimiter, pos -1)) + 1),
               delimiter, '');

    IF ret = '' THEN
        SET ret = NULL;
    END IF;

    RETURN ret;
END$$

DELIMITER ;

2. How to use:

-- 假设有一张表叫‘student’存了两个字段，姓名'name'、爱好'hobbys'，
-- 爱好列的数据格式为‘唱歌,跳舞,rap,篮球’
-- 要取出学生的第一个爱好'唱歌'的sql如下：

select  name,split(hobbys, ',', 1) from student