Question

我有以下代码

 Dim cmd As New MySqlCommand("SELECT IdNumber, COUNT(DISTINCT date) AS 'Attendance' FROM record WHERE MONTH(date) = MONTH(CURRENT_DATE()) AND YEAR(date) = YEAR(CURRENT_DATE()) GROUP BY idNumber ", cn)

    Dim i As MySqlDataReader = cmd.ExecuteReader()
    While i.Read
        Label1.Text = i("SUM(Attendance)")
        i.Close()
    End While

我需要在标签中显示COUNT列SUM，但是当我运行代码时，我收到以下错误：

'无法在结果中找到指定的列：SUM（出勤）'

在代码中生成COUNT列（出勤）以在特定日期期间获取表记录中的特定COUNT项并返回以下内容：

+----------+------------+
| idNumber | Attendance |
+-----------------------+
| 88383    | 4          |
| 64785    | 2          |
+-----------------------+

现在我想要对这些特定项目进行SUM并将它们显示在如下表格中：

标签= 6

Answer 1

如果您只需要总结每个IdNumber的所有不同日期，则无需选择idNumber，然后执行子查询以总结所有出勤率。

SELECT SUM(Attendance) as Label
from (
    SELECT COUNT(DISTINCT date) AS 'Attendance' 
    FROM record 
    WHERE MONTH(date) = MONTH(CURRENT_DATE()) 
    AND YEAR(date) = YEAR(CURRENT_DATE()) 
    GROUP BY idNumber
     );

 Result:
   Label
   6

如何求和COUNT列并在Label中显示答案

1 个答案: