reteiving data from my database

i have a problem in retrieving data from my database . i use those scripts bellow to read the database and to select data from it

public ArrayList ReadFullTable (string tableName)
    {
        string query;
        query = "SELECT * FROM " + tableName;
        dbcmd = dbcon.CreateCommand ();
        dbcmd.CommandText = query;
        reader = dbcmd.ExecuteReader ();
        ArrayList readArray = new ArrayList ();
        while (reader.Read())
        {
            ArrayList lineArray = new ArrayList ();
            for (int i = 0; i < reader.FieldCount; i++)
            {
                lineArray.Add (reader.GetValue (i));
            } // This reads the entries in a row
            readArray.Add (lineArray); // This makes an array of all the rows
        }
        return readArray; // return matches
    }
public string QueryString(string tablename, string column, string col_name, string value)
    {
                string text = "Not Found";
                string query;
                query = "SELECT " + column + " FROM " + tablename + " WHERE " + col_name + "='" + value + "'";  
                dbcmd = dbcon.CreateCommand ();
                dbcmd.CommandText = query;
                reader = dbcmd.ExecuteReader ();
 
        if(reader.Read())
        text = reader.GetString(0);
        else
            Debug.Log("QueryString - nothing to read...");
        reader.Close();
        dbcon.Close();
        return text;
    }

and i have another script

private string firstName = "First Name";
    private string  lastName = "Last Name";
    private string get = "GET";
    private string find = "FIND";
    private int DatabaseEntryStringWidth = 100;
    private Vector2 scrollPosition ;
    private ArrayList databaseData = new ArrayList ();
   
    // This GUI provides us with a way to enter data into our database
    //  as well as a way to view it
    void OnGUI ()
    {
        GUI.Box (new Rect (25, 25, Screen.width - 50, Screen.height - 50), "");
        GUILayout.BeginArea (new Rect (50, 50, Screen.width - 100, Screen.height - 100));
        // This first block allows us to enter new entries into our table
        GUILayout.BeginHorizontal ();
        firstName = GUILayout.TextField (firstName, GUILayout.Width (DatabaseEntryStringWidth));
        lastName = GUILayout.TextField (lastName, GUILayout.Width (DatabaseEntryStringWidth));
        get = GUILayout.TextField (get, GUILayout.Width (DatabaseEntryStringWidth));
        find = GUILayout.TextField (find, GUILayout.Width (DatabaseEntryStringWidth));
        GUILayout.EndHorizontal ();
       
        if (GUILayout.Button ("Add to database"))
        {
            // Insert the data
            InsertRow (firstName, lastName);
            // And update the readout of the database
            databaseData = ReadFullTable ();
 
        }
        // This second block gives us a button that will display/refresh the contents of our database
        GUILayout.BeginHorizontal ();
        if (GUILayout.Button ("Read Database"))
        {
            databaseData = ReadFullTable ();
       
        }
        if (GUILayout.Button ("Clear"))
        {
            databaseData.Clear ();
        }
        GUILayout.EndHorizontal ();
       
        GUILayout.Label ("Database Contents");
        scrollPosition = GUILayout.BeginScrollView (scrollPosition, GUILayout.Height (100));
        foreach (ArrayList line in databaseData)
        {
            GUILayout.BeginHorizontal ();
            foreach (object s in line)
            {
                GUILayout.Label (s.ToString (), GUILayout.Width (DatabaseEntryStringWidth));
            }
            GUILayout.EndHorizontal ();
        }
       
        GUILayout.EndScrollView ();
        if (GUILayout.Button("search"))
            {
            get = GetDefinitation(find);
            databaseData = ReadFullTable();
            }
        if (GUILayout.Button ("Delete All Data"))
        {
            DeleteTableContents ();
        databaseData = ReadFullTable ();
        }
       
        GUILayout.EndArea ();
    }
   
    // Wrapper function for inserting our specific entries into our specific database and table for this file
    private void InsertRow (string firstName, string lastName)
    {
        string[] values = new string[]{("'" + firstName + "'"), ("'" + lastName + "'")};
        db.InsertInto (TableName, values);
    }
   
    // Wrapper function, so we only mess with our table.
    private ArrayList ReadFullTable ()
    {
        return db.ReadFullTable(TableName);
    }
    public string GetDefinitation(string value)
    {
        return db.QueryString(TableName,"lastName","firstName", value);
    }
    // Another wrapper function...
    private void DeleteTableContents ()
    {
        db.DeleteTableContents (TableName);
    }
}

all the button works fine but the problem is in the button called 'search' when i click on it i have an error "SqliteSyntaxException: out of memory" i can't find where the problem is ?!! can anyone help me please ?! thank you