如果vb.net中不存在则更新

Question

Can anyone help me to fix my query. I want to update my data if the syscode is not exist but when I try to update sysdesc it failed because the syscode exist already.

    Dim query As String
    Dim rowsAffected As Integer
    query = "UPDATE tbl_sysname SET syscode = @code, sysdesc = @desc " & _
        "WHERE id = @id AND NOT EXISTS  (SELECT syscode FROM tbl_sysname WHERE " & _
        "syscode = @code) "

    cmd = New SqlCommand(query, cn)
    cmd.Parameters.Add("@code", SqlDbType.VarChar).Value = txtCode.Text
    cmd.Parameters.Add("@desc", SqlDbType.VarChar).Value = txtDesc.Text
    cmd.Parameters.Add("@id", SqlDbType.VarChar).Value = lblId.Text

    rowsAffected = cmd.ExecuteNonQuery
    'MsgBox(rowsAffected)

    If rowsAffected >= 1 Then
        'reader = cmd.ExecuteReader
        MsgBox("Update Successfully")
        LVSysName.Items.Clear()
        'reader.Close()
        GetLvData() 'This will display the data of LvSysName
    Else
        MsgBox("Failed to Update")
    End If

I want to avoid the duplication of syscode at the same time i can update sysdesc . Help me to fix my query or give me a suggestion on what should I do

Answer 1

You need to use two UPDATE statements for this. There is no way to do it in one go.

UPDATE tbl_sysname 
SET syscode = @code
WHERE id = @id AND 
  NOT EXISTS  (SELECT syscode FROM tbl_sysname WHERE syscode = @code)

UPDATE tbl_sysname 
SET sysdesc = @desc
WHERE id = @id