Question

我有一个名为people

的数据库表

 People
peopleID peopleName relationship customerID
1         A          aunty         1
2         B          aunty         1
3         C          second uncle  1
4         D          aunty         2

我如何计算customerID = 1的人数，如果关系相同，则计为1

所以从上面的数据库表中，我应该得到3的结果并将3的结果放在gridview中的Label1中？

我可以获得customerID = 1的唯一的计数值但我无法弄清楚如果关系部分我将如何计算

 Protected Sub GridView2_RowDataBound(sender As Object, e As 
System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView2.RowDataBound
        If e.Row.RowType = DataControlRowType.DataRow Then
            'Do your processing here...

            Dim txt As TextBox = DirectCast(e.Row.FindControl("Label1"), TextBox)
            Dim adapter As New SqlDataAdapter
            Dim ds As New DataSet
            'Dim sql As String

            Dim connectionString = ConfigurationManager.ConnectionStrings("ProjData").ConnectionString
            Dim myConn As New SqlConnection(connectionString)

            Dim cmd = "Select * From People Where customerID='" & Session("customerID") & "' "

            ' Dim myCmd As New SqlCommand(cmd, myConn)

            Try
                myConn.Open()
                Dim myCmd As New SqlCommand(cmd, myConn)
                adapter.SelectCommand = myCmd
                adapter.Fill(ds, "People")
                adapter.Dispose()
                myCmd.Dispose()
                txt.Text = ds.Tables(0).Rows.Count



            Catch ex As Exception
                MsgBox("Can not open connection ! ")
            End Try
        End If
    End Sub

Answer 1

您应该将SqlConnection包装在using语句中（不确定如何在VB中执行此操作）。在您的示例中，您不会关闭连接，using语句会自动为您执行此操作（替代方法是在finally块中关闭连接）

Answer 2

当我正确理解您的问题时，以下SQL语句应该根据您的需要为您提供计数。

Select count(peopleID) 
From People 
Where customerID = 1 
Group by relationship, customerID

如果此答案无法解决您的问题，请在您的问题中添加更多信息。

Answer 3

在您的代码中，您获取所有行，然后计算它们。您还可以执行将计算服务器上的行数的查询。这会表现得更好！

string sql = "SELECT COUNT(*) FROM People Where customerID='" & Session("customerID") & "' "
...
int rowCount = myCmd.ExecuteScalar();

如果要计算具有相同关系的行数，则必须使用分组。

您必须将sql更改为：

string sql = 'SELECT COUNT(peopleId) FROM People Where customerID='" & Session("customerID") & "' "GROUP BY relationship, customerId"

如何统计数据库中的记录？

3 个答案: