如何在Mysql中SUM重复COUNT值

Question

我有这段代码：

Const SQLExpression As String = "SELECT site.siteid AS 'SITE ID', site_name AS 'SITE',  COUNT(DISTINCT date) AS 'Attendance', 75 * (SELECT COUNT(DISTINCT date) AS 'Attendance') AS 'Total' FROM record LEFT JOIN learner on record.idNumber = learner.idNumber LEFT JOIN site ON learner.siteid=site.siteid WHERE MONTH(date) = MONTH(CURRENT_DATE()) AND YEAR(date) = YEAR(CURRENT_DATE()) GROUP BY record.idNumber "

它返回以下数据：Table

我想获得以下内容：

+----------+--------------------------------+
| SITE ID | SITE              | Attendance  |
+-------------------------------------------+
| 314     | Broad Market1     |    34       |
| 254     | Catherine Booth.. |    36       |
| 289     | Ceter for Entrep..|    27       |
| 330     | Climamark Morem.. |     7       |
+-------------------------------------------+

我尝试过以下代码：

"SELECT siteid AS 'SITE ID', site_name AS 'SITE', SUM(DISTINCT Attendance) AS 'Attendance' FROM (SELECT  COUNT(DISTINCT record.date)AS 'Attendance' FROM record LEFT JOIN learner on record.idNumber = learner.idNumber LEFT JOIN site ON learner.siteid=site.siteid WHERE MONTH(date) = MONTH(CURRENT_DATE()) AND YEAR(date) = YEAR(CURRENT_DATE()) GROUP BY record.idNumber) As Attendance, site GROUP BY siteid "

我得到以下数据：TableResult

Answer 1

假设在表站点中您拥有主键ID，您应该使用内部联接INNER JOIN站点Attendance.siteid = site.id（而不是交叉联接（出勤，没有站点的站点））

  "SELECT siteid AS 'SITE ID'
      , site_name AS 'SITE'
      , SUM(DISTINCT Attendance) AS 'Attendance' 
  FROM (
      SELECT  COUNT(DISTINCT record.date) AS 'Attendance' 
      FROM record 
      LEFT JOIN learner on record.idNumber = learner.idNumber 
      LEFT JOIN site ON learner.siteid=site.siteid 
      WHERE MONTH(date) = MONTH(CURRENT_DATE()) 
      AND YEAR(date) = YEAR(CURRENT_DATE()) 
      GROUP BY record.idNumber ) As T_Attendance
      INNER JOIN site T_Attendance.siteid = site.id
      GROUP BY siteid "