how to check for duplicate entry in database

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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

Posted 7-May-13 0:55am

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[no name] 7-May-13 7:02am

You write a query....

Johnny J. 7-May-13 9:14am

Helpful. Why bother writing a comment at all?

[no name] 7-May-13 21:35pm

Mostly because it directly answers the almost-but-not-quite question.

[no name] 7-May-13 7:03am

what query..??

2 solutions

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KM Perumal · Answer 1 · 2013-05-07T01:05:00

Solution 1

C#

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");
               }

Posted 7-May-13 1:05am

KM Perumal

Comments

Johnny J. 7-May-13 9:13am

A few comments:
1) You shouldn't instanciate an SqlDataAdapter and a DataSet just for this - it uses unnecessary memory
2) You shouldn't concatenate the query using "+" or "&" - it makes the code vulnerable to sql injections. You should use Sql Parameters

KM Perumal 8-May-13 0:43am

I ve given for example only Johnny

Johnny J. · Answer 2 · 2013-05-07T03:11:00

VB

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