事件调度程序计入结果的条件

Question

我有以下查询我想更新数据库，如果计数是唯一的1.我已经在事件调度程序mysql中创建了所有这个事件。但是有一些我无法识别的问题。请尽可能帮助我，查询如下：

SELECT user_id, count(*) as cnt from auction_details a JOIN products p where p.product_id = a.product_id AND p.end_time ='2018-09-12 08:35:30' GROUP by bidprice order by bidprice

报价价格应该是在事件日程表中更新表格的唯一方式

我想在事件调度程序中发生这种情况。我在事件调度程序中的想法如下：

DELIMITER |
DO
BEGIN 
DECLARE cnt AS INT;
SELECT user_id, count(*) as cnt from auction_details a JOIN products p where p.product_id = a.product_id AND p.end_time ='2018-09-12 08:35:30' GROUP by bidprice order by bidprice DESC LIMIT 1;    
IF cnt=1 THEN

SET @userid = SELECT user_id from auction_details a JOIN products p where p.product_id = a.product_id AND p.end_time ='2018-09-12 08:35:30' GROUP by bidprice order by bidprice DESC LIMIT 1;    
update products p join auction_details a on a.product_id = p.product_id join users u on u.user_id = a.user_id set p.winner = @userid WHERE p.end_time ='2018-09-12 08:35:30';
END IF;    

结束| DELIMITER;

期望的输出应该从查询中获得具有唯一计数的用户id，即1并更新products表并将获胜者设置为该用户id。

Answer 1

你需要ON clausule而不是WHERE，还需要GROUP BY user_id

SELECT user_id, count(*) as cnt 
from auction_details a 
JOIN products p 
  ON p.product_id = a.product_id 
  AND p.end_time ='2018-09-12 08:35:30' 
GROUP by user_id
order by user_id