如何检查数据库中的重复条目

问题描述：

大家好

请告诉我如何在插入数据之前检查数据库列中的重复条目。

i有一个名为company的列姓名（不是主键）

谢谢

Hi all

Please tell me how do i check duplicate entry in databse column before inserting the data.
i have column called company name(not a primary key)

thank you

答

SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM [company] Where companyname='" + Textbox.Text.Trim() + "'", connection);
              DataSet ds = new DataSet();
              da.Fill(ds);
              if (ds.Tables[0].Rows.Count == 0)
              {
                 MessageBox.Show("Company name Not found");
              }else
              {
                  MessageBox.Show("Company name Already exist");
               }

Public Function CompanyNameExists(ByVal companyName As String) As Boolean
    Dim query As String = "SELECT Count(*) FROM [yourtable] WHERE CompanyName=@CompanyName"
    Dim rowCount As Integer

    Using conn As New SqlConnection("your sql connection string")
        conn.Open()

        Using comm As New SqlCommand(query, conn)
            comm.Parameters.AddWithValue("@CompanyName", companyName)

            rowCount = Convert.ToInt32(comm.ExecuteScalar())
        End Using
    End Using

    Return (rowCount > 0)
End Function

如何检查数据库中的重复条目

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