Question

mysql使用左连接的SELECT查询不会产生我期望的结果。我希望有人可以告诉我或指出我正确的方向，

我正在尝试构建一个查询，我从“users”表中获取所有用户名从主表中获取他们为特定日期花费的所有时间的总和。我已经使用了左连接，但我没有按预期得到结果。

    Sub Joining()
    Dim N As Long, i As Long, r1 As Range, r2 As Range
 Dim z As Long
 Dim arr() As Variant
 z = 1

With Activesheet
    N = .Cells(Rows.Count, "A").End(xlUp).Row
    For i = 1 To N
        If .Cells(i, "B").Value Like "Summary*" Then
            arr = .Range(.Cells(i, "A"), .Cells(i, "H")).Value
            .Cells(z, "B").Value = Join(arr, " ")
            z = z + 1
        End If
    Next i
End With

主表

 SUM(m.time_spent) as sum_total_time
 FROM master as m
  LEFT OUTER JOIN users as u ON u.user_id = m.user_id
   WHERE m.date_created >= '2016-05-09'
  AND m.date_created <= '2016-05-13'
 GROUP BY name
 ORDER BY name

用户表

master_id       user_id         time_spent               date_created
1                     1              40                   2016-05-01
2                     2             36                   2016-05-02
3                     3              56                   2016-05-03
4                     2             33                   2016-05-03
5                     1              32                   2016-05-05
nth                 nth       nth number                    nth date

我希望输出结果如下所示：

user_id            first_name            last_name
1                     James                 Green
2                     Robert                 Cox 
3                    Andy                    Roger
etc                   etc                    etc

Answer 1

您必须直接从主表中选择数据，逐个用户地计算总和。然后，您可以将此结果与用户表连接，以获取有关该用户的所有信息。

Answer 2

可能是日期转换问题..

 SUM(m.time_spent) as sum_total_time
 FROM master as m
  LEFT OUTER JOIN users as u ON u.user_id = m.user_id
   WHERE m.date_created >=STR_TO_DATE( '2016-05-09', '%Y-%m-%d)

和/或你还有不完整的sql

SUM(m.time_spent) as sum_total_time
 FROM master as m
  LEFT OUTER JOIN users as u ON u.user_id = m.user_id
   WHERE m.date_created >= '2016-05-09'
  AND m.date_created  // this condition don't match with nothing.. 
                      // could be you forgot a part

更新1
如果你想要用户总计那么

   select u.id,   u.name, SUM(m.time_spent) as sum_total_time
   FROM master as m
   Inner  JOIN users as u ON u.user_id = m.user_id
   WHERE m.date_created >=STR_TO_DATE( '2016-05-09', '%Y-%m-%d)
   AND m.date_created <= =STR_TO_DATE('2016-05-13'', '%Y-%m-%d)
   Group by u.id

Mysql查询LEFT JOIN意外结果

2 个答案: