在插入之前在Access數據庫中檢查重複

Question

在找到解決方案之前一直清醒。有沒有辦法在插入值之前檢查我的Access數據庫上的重複內容，並向我發送已有記錄的消息。這裏是我的代碼，我不知道在哪裏以及如何檢查它

Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click 

      If txtCat.Text = "" Then 
       MsgBox("Please Complete the Information Needed") 
       txtCat.Focus() 


      Else 
       If MsgBox("Are you sure you want to Add Category?", MsgBoxStyle.Question + MsgBoxStyle.YesNo, "WARNING") = MsgBoxResult.Yes Then 

        Dim DBC As New OleDbCommand 
        With DBC 
         .Connection = conn 
         .CommandText = "INSERT INTO tbl_category(Category) VALUES('" & txtCat.Text & "')" 
         .ExecuteNonQuery() 
        End With 
        MsgBox("Category Added!", MsgBoxStyle.Information + MsgBoxStyle.OkOnly, "SUCCESS") 

        Call CatList() 

        txtCat.Text = "" 
        txtCat.Enabled = False 
        btnSave.Enabled = False 

        Call CatCombo() 


       End If 
      End If 

     End Sub 

這是我第一次來檢查重複的，這就是爲什麼我不知道該怎麼

Answer 1

像這樣的工作：

"INSERT INTO tbl_category(Category) VALUES('" & txtCat.Text & "') WHERE NOT EXISTS (Select '8' from tbl_category where Category = + " & txtCat.Text & + " 

當然，這並不是最好的做法。這種格式容易受到SQL注入的影響。