Question

Name      Username    Day worked  Time period  
----------------------------------------------
John Doe  john        Sunday      8
Tom       tom         Monday      10
Jane Doe  jane        Tuesday     5
John Doe  john        Friday      9

查询：

SELECT username FROM table WHERE (day_worked='Sunday' AND time_period>5) AND (day_worked='Friday' and time_period>8)

我在这里申请两个栏目的条件，周日工作时间超过5小时，周五工作时间超过8小时。显然，John Doe（用户名：john）符合条件，应该输出。

然而，这不会返回任何东西。可能是我使用的逻辑是错误的。有什么想法吗？

Answer 1

你可以通过一些交叉制表魔术来做到这一点。首先，在周日和周五之间交叉制表所有用户：

SELECT
  username,
  SUM(CASE WHEN `Day worked` = 'Sunday' THEN `Time Period` END) As Sunday,
  SUM(CASE WHEN `Day worked` = 'Friday' THEN `Time Period` END) AS Friday
FROM table
GROUP BY username

此查询将产生以下内容：

username  Sunday  Friday
--------  ------  ------
jane      NULL    NULL
john      8       9
tom       NULL    NULL

通过将此结果推送到子查询中，您可以轻松地选出周日工作时间超过5小时且周五工作时间超过8小时的人员：

 SELECT username
 FROM (
   SELECT
     username,
      SUM(CASE WHEN `Day worked` = 'Sunday' THEN `Time Period` END) As Sunday,
      SUM(CASE WHEN `Day worked` = 'Friday' THEN `Time Period` END) AS Friday
    FROM table
    GROUP BY username
  ) SunFri
WHERE SunFri.Sunday > 5 AND SunFri.Friday > 8

Answer 2

SELECT username 
  FROM table 
 WHERE (day_worked='Sunday' AND time_period>5)         
    OR (day_worked='Friday' and time_period>8) 
 GROUP 
    BY username
HAVING COUNT(*) = 2

Answer 3

您可以检查此查询是否为您提供了所需的结果

SELECT username FROM table 
INNER JOIN table T2 ON table.Username = T2.Username AND (day_worked='Friday' and time_period>8)
WHERE (day_worked='Sunday' AND time_period>5)

最好发布一个sqlfiddle供我们使用。

如何根据两行条件选择列值？

3 个答案: