平時工作中我們會遇到主從層次關係的結構資料，我們需要把資料取出來並且提現出層級就像樹形結構一樣，比如這樣的結構：

資料庫表結構如下，有個parent_id和sub_id，就是把兩者的關係儲存起來。

id為768的下面有769,770,771,772,780,781資料，同時這些資料下面有可能有其它的資料，我們要查出768下面的所有資料可以使用mysql的函式來獲取一條資料下面的子集

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);
			# 迴圈遞迴
      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
 

這個函式的作用就是獲取768下面的所有子集的id，我們使用navicat 查詢這個函式

select getMaterialBomChildList(768) as subIds;

就能得到所有的子集

 我們在執行查詢方法得到所有的資料

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

利用儲存過程查詢出結果

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)
		-- 避免死迴圈
		AND @lid<10 	-- 簡化處理
		-- 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
 

查詢結果

call getBomlList(768);