Question

列的默认值是否可以作为查询结果，只要查询该值，该值就会自动更新？

我有一个带有成员和取消表的数据库，我希望将members.NumberOfCancellations值自动填充为下面的伪查询的结果：

从取消的所有取消中选择所有取消。从今天起不到31天，其中cancellations.memberid等于$ phpvariable

我知道这可以用php和select / update脚本完成，但我希望phpmyadmin可能有这个功能吗？

______________________________________________________________
|memberid  |   firstname  | lastname  | numberofcancellations|
______________________________________________________________
|1         |   john       | doe       | resultofquery(= 2)   |  
|2         |  Dave        | Smith     | resultofquery (=1)   |
______________________________________________________________

___________________________________
|id    |memberid  |   date    | time  | group |
___________________________________
|1     |1         |2016-04-19 | 08:00 | 1     |
|2     |2         |2016-04-18 | 13:00 | 4     |
|3     |1         |2016-04-15 | 18:00 | 3     |
_______________________________________________

Answer 1

如果您的members表还没有取消计数列，请添加：

ALTER TABLE members ADD numberofcancellations int AFTER lastname;

现在，您可以使用取消计数更新members：

UPDATE members t1 LEFT JOIN
(
    SELECT memberid, COUNT(*) AS numberofcancellations
    FROM cancellations
    WHERE date BETWEEN CURDATE() - INTERVAL 30 DAY AND CURDATE()
    GROUP BY memberid
) t2
   ON t1.memberid = t2.memberid
SET t1.numberofcancellations = COALESCE(t2.numberofcancellations, 0)

您需要运行此查询一次以初始填充新列。如果您想更新单个成员，则可以在WHERE语句中添加UPDATE条件：

UPDATE members t1 LEFT JOIN
(
    SELECT memberid, COUNT(*) AS numberofcancellations
    FROM cancellations
    WHERE date BETWEEN CURDATE() - INTERVAL 30 DAY AND CURDATE()
    GROUP BY memberid
) t2
   ON t1.memberid = t2.memberid
SET t1.numberofcancellations = COALESCE(t2.numberofcancellations, 0)
WHERE t1.memberid = 1   -- or whatever value you want

默认MySQL值是查询的结果

1 个答案: