Database

static public DataTable query_search(string sqlite_query, SQLiteParameter[] parameters)
 {
     SQLiteConnection sqlite_conn = new SQLiteConnection("Data Source=test.db;Version=3;Compress=True;Synchronous=Full;");

     sqlite_conn.Open();
     SQLiteCommand sqlite_cmd;
     sqlite_cmd = sqlite_conn.CreateCommand();
     sqlite_cmd.CommandText = sqlite_query;
     SQLiteDataReader sqlite_datareader;

     sqlite_cmd.Parameters.AddRange(parameters);
     sqlite_datareader = sqlite_cmd.ExecuteReader();

     DataTable returnTable = new DataTable();
     returnTable.Load(sqlite_datareader);

     writedebug(returnTable.Rows.Count.ToString());

     sqlite_conn.Close();
     sqlite_datareader.Close();
     return returnTable;
 }

private void button1_Click(object sender, EventArgs e)
{
    if (search.Text.Trim() != "")
    {

        SQLiteParameter[] param = {
            new SQLiteParameter("%@search%", "paul") //used direct string for debug //search.Text)
        };

        customerList.Rows.Clear();

        DataTable searchinfo = database.query_search("SELECT id, firstname, lastname FROM customers WHERE firstname LIKE '@search' OR lastname LIKE '@search'", param);

        MessageBox.Show(searchinfo.Rows.Count.ToString());

        foreach (DataRow row in searchinfo.Rows)
        {
            customerList.Rows.Add(row[0].ToString(), row[1].ToString() + " " + row[2].ToString());
        }
    }
}

i have Two Database in two different servers i want to join two tables from this two Databases

 i have no relation between them but just a column wich contain information about the other database 

Ex : Database1.dbo.informationCity contain a column named Specification and have this information: 
14042020111925_GMS3439_09_04_2020-04_48.xml_6456.zip 

i want to extract from this column just this number 3439 because with this number i can rely the other database 

Ex : Database2.dbo.city contain a column named cityID : 3439 

any body have an idea how to do that ? 
i tried this Sql request but it did not work

    <pre lang="SQL">SELECT 
    *
      FROM [mo].[dbo].[Database1]
      INNER JOIN [Database2].[dbo].[city ] ON substring([Specification], CHARINDEX('GMS', [Specification ]) + 3,4) = 
      [Database2].[dbo].[city ].[cityID]