SQL Count 不计算数据库中数据的行数

Question

我在下面创建了 sub 来计算 SQL 服务器表中的数据出现次数，其中特定值出现在同一个表中。 但是，它不符合我的要求。 子尝试计算表中特定诊所名称的用户数。 但是，它只计为 0。

    Private Sub chUser()

    conn = New SqlConnection(conStr)
    conn.Open()
    myConn.clName = clNameDGV.SelectedCells.Item(0).Value
    MsgBox(myConn.clName)
    Dim comStr As String = "Select Count(*) as clName from Login_Detail Where Clinic_Name = '" & myConn.clName & "'"
    Dim comm As New SqlCommand(comStr, conn)
    Dim i As Integer = comm.ExecuteScalar()

    If i = 0 Then
        If MessageBox.Show("No User Information found for '" + clNameDGV.SelectedCells.Item(0).Value + "'." + vbNewLine + "Do you want to enter new user details ?", "No Users Found", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = vbYes Then
            Dim nf As New CreateUser
            nf.TopMost = True
            nf.ShowDialog(Me)
        End If
    Else
        Dim nf1 As New LoginForm
        nf1.TopMost = True
        nf1.ShowDialog(Me)

    End If
    conn.Close()

End Sub

Answer 1

试试下面的代码：

Private Sub chUser()
    conn = New SqlConnection(conStr)
    conn.Open()
    myConn.clName = clNameDGV.SelectedCells.Item(0).Value
    MsgBox(myConn.clName)
    Dim comStr As String = "Select Count(*) as clName from Login_Detail Where Clinic_Name = N'" & myConn.clName & "'"
    Dim comm As New SqlCommand(comStr,conn)
    //Dim i As Integer = comm.ExecuteScalar()
    Dim dt As DataTable  
    Dim da As New SqlDataAdapter(comm)
    da.Fill(dt)
    Dim i As Integer = Integer.parse(dt.Rows(0)(0).ToString())
    If i = 0 Then
        If MessageBox.Show("No User Information found for '" + clNameDGV.SelectedCells.Item(0).Value + "'." + vbNewLine + "Do you want to enter new user details ?", "No Users Found", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = vbYes Then
            Dim nf As New CreateUser
            nf.TopMost = True
            nf.ShowDialog(Me)
        End If
    Else
        Dim nf1 As New LoginForm
        nf1.TopMost = True
        nf1.ShowDialog(Me)

    End If
    conn.Close()

End Sub