递归调用自身的mysql存储过程

Question

我有下表：

id | parent_id | quantity
-------------------------
1  | null      | 5
2  | null      | 3
3  | 2         | 10
4  | 2         | 15
5  | 3         | 2
6  | 5         | 4
7  | 1         | 9

现在我需要 mysql 中的一个存储过程，它递归地调用自身并返回计算的数量。 例如，id 6 有 5 作为父级，有 3 作为父级，有 2 作为父级。 所以我需要计算 4 * 2 * 10 * 3 ( = 240) 作为结果。

我对存储过程相当陌生，将来不会经常使用它们，因为我更喜欢将业务逻辑放在程序代码中而不是放在数据库中。但在这种情况下我无法避免。

也许 mysql 大师（就是你）可以在几秒钟内拼凑出一个工作语句。

Answer 1

它仅在 mysql 版本 >= 5 中工作，

存储过程声明是这样的，

您可以对其进行一点改进，但​​是可以工作：

DELIMITER $

CREATE PROCEDURE calctotal(
   IN number INT,
   OUT total INT
)

BEGIN

   DECLARE parent_ID INT DEFAULT NULL ;
   DECLARE tmptotal INT DEFAULT 0;
   DECLARE tmptotal2 INT DEFAULT 0;

   SELECT parentid   FROM test   WHERE id = number INTO parent_ID;   
   SELECT quantity   FROM test   WHERE id = number INTO tmptotal;     

   IF parent_ID IS NULL
    THEN
    SET total = tmptotal;
   ELSE     
    CALL calctotal(parent_ID, tmptotal2);
    SET total = tmptotal2 * tmptotal;   
   END IF;

END$

DELIMITER ;

调用就像
（设置这个变量很重要）：

SET @@GLOBAL.max_sp_recursion_depth = 255;
SET @@session.max_sp_recursion_depth = 255; 

CALL calctotal(6, @total);
SELECT @total;

Answer 2

查看 Mike Hillyer 撰写的管理 MySQL 中的分层数据。

它包含处理分层数据的完整示例。

Answer 3

如何避免程序：

SELECT quantity from (
 SELECT @rq:=parent_id as id, @val:=@val*quantity as quantity from (
  select * from testTable order by -id limit 1000000 # 'limit' is required for MariaDB if we want to sort rows in subquery
 ) t # we have to inverse ids first in order to get this working...
 join
 ( select @rq:= 6 /* example query */, @val:= 1 /* we are going to multiply values */) tmp
 where id=@rq
) c where id is null;

查看 Fiddle！

注意！如果行的 parent_id>id 则此方法不起作用。

干杯!

Answer 4

DELIMITER $
CREATE DEFINER=`arun`@`%` PROCEDURE `recursivesubtree`( in iroot int(100) , in ilevel int(110) , in locid int(101) )
BEGIN
  DECLARE irows,ichildid,iparentid,ichildcount,done INT DEFAULT 0;

  DECLARE cname VARCHAR(64);
  SET irows = ( SELECT COUNT(*) FROM account WHERE parent_id=iroot and location_id=locid );
  IF ilevel = 0 THEN
    DROP TEMPORARY TABLE IF EXISTS _descendants;
    CREATE TEMPORARY TABLE _descendants (
      childID INT, parentID INT, name VARCHAR(64), childcount INT, level INT
  );
  END IF;
  IF irows > 0 THEN
    BEGIN
      DECLARE cur CURSOR FOR
        SELECT
          f.account_id,f.parent_id,f.account_name,
          (SELECT COUNT(*) FROM account WHERE parent_id=t.account_id and location_id=locid ) AS childcount
        FROM account t JOIN account f ON t.account_id=f.account_id
        WHERE t.parent_id=iroot and t.location_id=locid 
        ORDER BY childcount<>0,t.account_id;
      DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;
      OPEN cur;
      WHILE NOT done DO
        FETCH cur INTO ichildid,iparentid,cname,ichildcount;
        IF NOT done THEN
          INSERT INTO _descendants VALUES(ichildid,iparentid,cname,ichildcount,ilevel );
          IF ichildcount > 0 THEN
            CALL recursivesubtree( ichildid, ilevel + 1 );
          END IF;
        END IF;
      END WHILE;
      CLOSE cur;
    END;
  END IF;

  IF ilevel = 0 THEN
    -- Show result table headed by name that corresponds to iroot:
    SET cname = (SELECT account_name FROM account WHERE account_id=iroot and location_id=locid );
    SET @sql = CONCAT('SELECT   CONCAT(REPEAT(CHAR(36),2*level),IF(childcount,UPPER(name),name))',
                  ' AS ', CHAR(39),cname,CHAR(39),' FROM _descendants');
    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DROP PREPARE stmt;
  END IF;
END$
DELIMITER ;