Question

我有一个下面给出的表结构。

Name

必须自动生成包含CREATE TABLE `sample` ( `PK_ID` varchar(10) NOT NULL, `RQ_ID` varchar(10) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL, `BID_VAL` double NOT NULL DEFAULT '0', `max_bid` double NOT NULL, `Last_updated` datetime NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

的列max_bid

我需要一个触发器，它会在max(BID_VAL) group by RQ_ID

之后更新max_bid

谢谢。

Answer 1

您不能在导致触发器的同一个表中进行更新或插入，但您可以这样做：更新记录的max_bid，因为你插入它

DELIMITER ||
CREATE TRIGGER  `calculate_max_bid`  BEFORE insert ON `sample`  FOR EACH ROW 
begin 
DECLARE max_bid_val double;
SELECT 
    max(BID_VAL) into max_bid_val 
FROM sample 
WHERE 
RQ_ID = new.RQ_ID 
GROUP BY RQ_ID;
if max_bid_val > new.bid_val then
 SET new.max_bid = max_bid_val;
 ELSE 
  SET new.max_bid = new.BID_VAL; 
 end if;
END ||
DELIMITER ;

Answer 2

你可以像这样使用程序：

DELIMITER ||
CREATE PROCEDURE update_max ( 
 IN PK_ID_val varchar(10),
 IN RQ_ID_VAL varchar(10) ,
 IN BID_VAL_VAL double ,
 IN Last_updated_VAL datetime 
 )
BEGIN
DECLARE calcul_max_bid double;
 insert into sample 
        (PK_ID,RQ_ID,BID_VAL,MAX_BID,Last_updated)
  values (PK_ID_VAL,RQ_ID_VAL,BID_VAL_VAL,0,Last_updated_VAL);
  SELECT 
    max(BID_VAL) into calcul_max_bid 
    FROM sample 
    WHERE 
    RQ_ID = RQ_ID_VAL
  GROUP BY RQ_ID;
 update sample set max_bid = calcul_max_bid where RQ_ID=RQ_ID_val;
END ||
DELIMITER ;

所以代替执行insert直接调用此过程

call update_max('A','RQ_1',12.0,'2016-12-12');

每次插入后更新一列

2 个答案: