How to Remove Duplicate OUTPUT in SQL?

Question

I have a problem with a ComboBox, its items are being duplicated. How can I prevent this situation? Here is some images:

Here is my code sample used to populate it:

string SelectQuery = "SELECT   Part , Model  FROM ctautoparts.nissanpart , ctautoparts.nissan   ;";

MySqlConnection sqlConn = new MySqlConnection(myConnectionString);
MySqlCommand cmdDatabase = new MySqlCommand(SelectQuery, sqlConn);
MySqlDataReader myReader;

try
{
    sqlConn.Open();
    myReader = cmdDatabase.ExecuteReader();
    // int model = myReader.GetOrdinal("model");
    //int model1 = myReader.GetOrdinal("part");
    while (myReader.Read())
    {

    //  string namethestore = myReader.IsDBNull(model)
    //   ? string.Empty
    //  : myReader.GetString("model");

    //   this.carmodel.Text = namethestore;

    //  string namethestore1 = myReader.IsDBNull(model)
    //  ? string.Empty
    // : myReader.GetString("parts");

    ///  this.carpart.Text = namethestore1;
    carmodel.Items.Add(myReader["Model"].ToString());

    carpart.Items.Add(myReader["Part"].ToString());

    }
}
catch (Exception msg)
{
    MessageBox.Show(msg.Message);
}

When you run the query from a native mysql prompt, do you get duplicates? — Mark Stewart
– Mark Stewart, Commented May 31, 2017 at 19:49

Hariraman Radhakrishnan · Accepted Answer · 2017-05-31 16:56:56Z

1

Add distinct to your select query, so that the duplicates will be removed

answered May 31, 2017 at 16:56

Hariraman Radhakrishnan

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5 Comments

Sigbin PInos Over a year ago

its still duplicate

Alisson Reinaldo Silva Over a year ago

How are you sure the problem is the query? What if OP is calling that function multiple times?

Sigbin PInos Over a year ago

what you mean OP? sorry im new

Alisson Reinaldo Silva Over a year ago

@SigbinPInos "Original Poster", take a look here.

Sigbin PInos Over a year ago

how can i stop calling them multiple times?

Alisson Reinaldo Silva · Accepted Answer · 2017-05-31 17:27:10Z

0

It looks your query is returning duplicated lines. I'd suggest executing them separatedely:

try
{
    // POPULATE MODELS
    string modelsQuery = "SELECT Model FROM ctautoparts.nissan;";
    using (MySqlConnection sqlConn = new MySqlConnection(myConnectionString))
    {
        using (MySqlCommand cmdDatabase = new MySqlCommand(modelsQuery, sqlConn))
        {
            sqlConn.Open();
            MySqlDataReader myReader = cmdDatabase.ExecuteReader();
            // int model = myReader.GetOrdinal("model");
            //int model1 = myReader.GetOrdinal("part");
            while (myReader.Read())
            {
                carmodel.Items.Add(myReader["Model"].ToString());
            }
        }
    }


    // POPULATE PARTS
    string partsQuery = "SELECT Part FROM ctautoparts.nissanpart;";
    using (MySqlConnection sqlConn = new MySqlConnection(myConnectionString))
    {
        using (MySqlCommand cmdDatabase = new MySqlCommand(partsQuery, sqlConn))
        {
            sqlConn.Open();
            MySqlDataReader myReader = cmdDatabase.ExecuteReader();
            // int model = myReader.GetOrdinal("model");
            //int model1 = myReader.GetOrdinal("part");
            while (myReader.Read())
            {
                carpart.Items.Add(myReader["Part"].ToString());
            }
        }
    }
}
catch (Exception msg)
{
    MessageBox.Show(msg.Message);
}

edited May 31, 2017 at 17:27

answered May 31, 2017 at 17:03

Alisson Reinaldo Silva

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5 Comments

Sigbin PInos Over a year ago

string SelectQuery = "SELECT Part , Model FROM ctautoparts.nissanpart , ctautoparts.nissan ;"; <-- thats my query

Alisson Reinaldo Silva Over a year ago

@SigbinPInos I edited my answer, I hadn't see your query. It's better and simple to execute two queries instead of only one, since you're not even doing an INNER JOIN.

Sigbin PInos Over a year ago

what does this mean? Severity Code Description Project File Line Error CS0246 The type or namespace name 'SqlDataReader' could not be found (are you missing a using directive or an assembly reference?) CTAUTOPARTS c:\users\kevin\documents\visual studio 2015\Projects\CTAUTOPARTS\CTAUTOPARTS\Addinvetory.cs 145

Alisson Reinaldo Silva Over a year ago

@SigbinPInos I forgot you're using MySQL. I edited my answer, just change all SqlConnection, SqlCommand and SqlDataReader to MySqlConnection, MySqlCommand and MySqlDataReader (respectively).

Sigbin PInos Over a year ago

BRO! THANK YOU SO MUCH!

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