sql递归查询子类

平时工作中我们会遇到主从层次关系的结构数据，我们需要把数据取出来并且提现出层级就像树形结构一样，比如这样的结构：

数据库表结构如下，有个parent_id和sub_id，就是把两者的关系保存起来。

id为768的下面有769,770,771,772,780,781数据，同时这些数据下面有可能有其它的数据，我们要查出768下面的所有数据可以使用mysql的函数来获取一条数据下面的子集

CREATE FUNCTION `getMaterialBomChildList`(`input_parent_id` integer) RETURNS varchar(1000) CHARSET utf8
BEGIN  
      DECLARE sChildList VARCHAR(1000);  
      DECLARE sChildTemp VARCHAR(1000);  
      SET sChildTemp = cast(input_parent_id as CHAR);
			# 循环递归
      WHILE sChildTemp is not null DO
        IF (sChildList is not null) THEN  
          SET sChildList = concat(sChildList,',',sChildTemp);  
				ELSE  
					SET sChildList = concat(sChildTemp);  
				END IF;
  
        SELECT group_concat(sub_id) INTO sChildTemp FROM bs_material_bom where FIND_IN_SET(parent_id,sChildTemp)>0;  
      END WHILE;  
      RETURN sChildList;  
    END

这个函数的作用就是获取768下面的所有子集的id，我们使用navicat 查询这个函数

select getMaterialBomChildList(768) as subIds;

就能得到所有的子集

 我们在执行查询方法得到所有的数据

select * from bs_material_bom where FIND_IN_SET(parent_id,getMaterialBomChildList(768));

利用存储过程查询出结果

CREATE PROCEDURE `getBomlList`(IN `mid` int)
BEGIN
	#Routine body goes here...
	DROP TEMPORARY TABLE IF EXISTS bomlist;
	DROP TEMPORARY TABLE IF EXISTS bomlist_copy;
	CREATE TEMPORARY TABLE IF NOT EXISTS bomlist(
		mid INTEGER NOT NULL,
		qty INT NOT NULL DEFAULT 0,
		lct  VARCHAR(1024) NULL,
		mpath VARCHAR(1024) NULL,
		lid INTEGER NOT NULL
	);
	CREATE TEMPORARY TABLE IF NOT EXISTS bomlist_copy(
			mid INTEGER NOT NULL,
			qty INT NOT NULL DEFAULT 0,
			lct  VARCHAR(1024) NULL,
			mpath VARCHAR(1024) NULL,
			lid INTEGER NOT NULL
		);

	-- init
	SET @lid = 1;
	DELETE FROM bomlist;
	DELETE FROM bomlist_copy;
	INSERT INTO bomlist(mid, qty, lct, mpath, lid) values(mid, 1, '', mid, @lid);
	INSERT INTO bomlist_copy(mid, qty, lct, mpath, lid) values(mid, 1, '', mid, @lid);

	-- get sub mtls
	WHILE
		EXISTS (SELECT 1 FROM bomlist_copy A INNER JOIN bs_material_bom B ON A.mid = B.parent_id WHERE A.lid = @lid)
		-- 避免死循环
		AND @lid<10 	-- 简化处理
		-- AND NOT EXISTS(SELECT 1 FROM bomlist_copy C LEFT JOIN bs_material_bom D ON C.mid = D.parent_id WHERE C.lid = @lid AND B.sub_id in (SELECT mid FROM bomlist))
	DO
		-- get sub mtls
		INSERT INTO bomlist(mid, qty, lct, mpath, lid) SELECT B.sub_id, B.qty, B.location, CONCAT(A.mpath, ',', B.sub_id), (@lid+1) AS new_lid FROM bomlist_copy A INNER JOIN bs_material_bom B ON A.mid = B.parent_id WHERE A.lid = @lid;
	
		-- avoid reopen temporaty table
		INSERT INTO bomlist_copy(mid, qty, lct, mpath, lid) SELECT * FROM bomlist WHERE lid = (@lid + 1);

		-- init next level
		SET @lid = @lid + 1;
	END WHILE;	

	SELECT A.*, B.material_code, B.description
	FROM bomlist A LEFT JOIN bs_materials B ON A.mid=B.id
	ORDER BY A.mpath;
END

查询结果

call getBomlList(768);