MySQL获得所有用户，无论他们是否有任何时间？

Question

试图吸引所有用户，无论他们是否有任何时间？我的LEFT OUTER JOIN仍无法正常工作..

    SELECT tblleaverequest.lqUser,
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 1 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jan',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 2 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Feb',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 3 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Mar',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 4 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Apr',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 5 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'May',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 6 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jun',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 7 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jul',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 8 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Aug',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 9 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Sep',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 10 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Oct',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 11 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Nov',
       SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 12 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Dec',
       SUM(tblleaverequest.lqHoursPL) AS PaidLeaveTotal

FROM      tblusers LEFT OUTER JOIN tblleaverequest ON tblleaverequest.lqUser = tblusers.username       

WHERE     (tblusers.clr_accrual = '1') AND (YEAR(tblleaverequest.lqStartDate) = YEAR(CURDATE())) 
GROUP BY tblusers.username

以下是我的结果，但我需要其他用户也没有时间。

Answer 1

不确定您的数据库架构，但似乎您可以将一个条件从WHERE移到ON子句

SELECT tblusers.username,
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 1 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jan',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 2 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Feb',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 3 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Mar',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 4 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Apr',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 5 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'May',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 6 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jun',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 7 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Jul',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 8 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Aug',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 9 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Sep',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 10 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Oct',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 11 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Nov',
   SUM(CASE WHEN DATE_FORMAT(tblleaverequest.lqStartDate, '%m') = 12 THEN (tblleaverequest.lqHoursPL) ELSE 0 END) AS 'Dec',
   SUM(tblleaverequest.lqHoursPL) AS PaidLeaveTotal

FROM      tblusers 
LEFT OUTER JOIN tblleaverequest 
ON tblleaverequest.lqUser = tblusers.username       
  AND (YEAR(tblleaverequest.lqStartDate) = YEAR(CURDATE())) 
WHERE     (tblusers.clr_accrual = '1') 
GROUP BY tblusers.username

Answer 2

WHERE ... (YEAR(tblleaverequest.lqStartDate) = YEAR(CURDATE()))

如果记录tblLeaveRequest中没有匹配项，则日期为null。由于null不能等于任何内容，因此这些记录将被删除。所以你基本上是将OUTER JOIN转换为INNER JOIN。将该比较移动到JOIN语句以保留OUTER JOIN。

<强>更新

请务必从tblusers获取用户名，因为tblleaverequest.lqUser值可能因OUTER JOIN而为空。

SELECT tblusers.username 
       , SUM(CASE ......)) AS Jan
       , ....