MySQL根據父節點id查詢所有子節點

方法一

<!--根據id查詢子節點-->
    <select id="sonId" parameterType="java.lang.String" resultType="com.tl.visual.model.SystemRelate">
        SELECT class_id FROM (
              SELECT t1.class_id,
              IF(FIND_IN_SET(parent_id, @pids) > 0, @pids := CONCAT(@pids, ',', class_id), 0) AS ischild
              FROM (
                   SELECT class_id,parent_id FROM 表名 t WHERE t.state = '01' ORDER BY parent_id, class_id
                  ) t1,
                  (SELECT @pids := #{要查詢的id}) t2
             ) t3 WHERE ischild != 0
    </select>

方法二

SELECT *  FROM (
		SELECT t1.*,
		IF(FIND_IN_SET(pid, @pids) > 0, @pids := CONCAT(@pids, ',', id), '0') AS ischild
		FROM (
		SELECT * FROM test2 AS t WHERE t.state = '01' ORDER BY t.id ASC
		) t1,
		(SELECT @pids := 'b1') t2
		) t3 WHERE ischild != '0'

替換的地方：
test2 替換成你的表名
pid 替換成你的父id
id 替換成你的主鍵id
state 組織狀態
b1 替換成你要查詢的主鍵id