mysql字符串分割操作

SELECT '1,2,3,4,5,6,7,8' FROM dual;

-- 列转行分割
SELECT DISTINCT SUBSTRING_INDEX(SUBSTRING_INDEX(a.path,',',b.help_topic_id + 1),',',-1)
FROM
(SELECT GROUP_CONCAT(REPLACE(path,'/',',')) AS path FROM department b WHERE department_type = 1) a
JOIN
mysql.help_topic b
ON b.help_topic_id < (LENGTH(a.path) - LENGTH(REPLACE(a.path,',','')) + 1);

-- 测试
SELECT DISTINCT SUBSTRING_INDEX(SUBSTRING_INDEX(a.path,',',b.help_topic_id + 1),',',-1) as path
FROM
(SELECT '1,2,3,4,5,6,7,8' as path FROM dual) a
JOIN
mysql.help_topic b
ON b.help_topic_id < (LENGTH(a.path) - LENGTH(REPLACE(a.path,',','')) + 1);

测试结果：