SQL Query doesn't work in asmx web service

Question

I made asmx web, to get data from oracle database. It works fine when I use a short query:

select * from dbrepn10.DDT_DA_DIRECTION_SV

But if I use long query like this:

SELECT XB_.R_OBJECT_ID, XB_.OBJECT_NAME, XB_.R_CREATION_DATE, XB_.R_MODIFY_DATE, XB_.R_MODIFIER, XB_.R_ACCESS_DATE, XB_.A_CONTENT_TYPE, 
    XB_.R_CONTENT_SIZE, XB_.OWNER_NAME, XB_.ACL_DOMAIN, XB_.ACL_NAME, XB_.R_CREATOR_NAME, BKB_.DSI_PAGE_COUNT, EKB_.DSS_REG_NUMBER, EKB_.DST_REG_DATE, EKB_.DSS_OBJECT_NAME_RU, MKB_.DSS_TITLE_RU, MKB_.DSS_TITLE_KK 
FROM dbrep36.DM_SYSOBJECT_S XB_, dbrep36.DDT_EAR_S BKB_, dbrep36.DDT_EAR_REG_S EKB_,dbrep36.DDT_DA_DIRECTION_S MKB_ 
WHERE (XB_.R_OBJECT_ID=MKB_.R_OBJECT_ID AND (XB_.R_OBJECT_ID=BKB_.R_OBJECT_ID AND (BKB_.R_OBJECT_ID=MKB_.R_OBJECT_ID AND (XB_.R_OBJECT_ID=EKB_.R_OBJECT_ID AND(BKB_.R_OBJECT_ID=EKB_.R_OBJECT_ID AND EKB_.R_OBJECT_ID=MKB_.R_OBJECT_ID)))))

My web service doesn't return a result. And there are no error messages.

What could be the reason ?

Code:

 public DataTable GetSpecificView(string query_string)
    {
        string host = WebConfigurationManager.AppSettings["host"].ToString();
        string port = WebConfigurationManager.AppSettings["port"].ToString();
        string servicename = WebConfigurationManager.AppSettings["servicename"].ToString();
        string user = WebConfigurationManager.AppSettings["user"].ToString();
        string password = WebConfigurationManager.AppSettings["password"].ToString();

        DataTable data = new DataTable();

        string connectionString = OracleConnString(host, port, servicename, user, password);
        OracleConnection con = new OracleConnection(connectionString);
        con.ConnectionString = connectionString;
        string result = "";
        try
        {
            con.Open();
            OracleCommand cmd = new OracleCommand(query_string, con);

            DataSet dataSet = new DataSet();
            new OracleDataAdapter(cmd).Fill(dataSet);
            if (dataSet.Tables.Count > 0)
            {
                data = dataSet.Tables[0];
            }
            con.Close();

        }
        catch (Exception ex)
        {
            result = ex.Message;
        }
        return data;
    }

Answer 1

Are you certain you are not getting an exception? Your catch loop isn't doing anything, it's just assigning the exception message to a string which doesn't appear to be logged anywhere.

Also, you should place the con.Close() call in a finally block as it won't be called if an exception is thrown.

Have you tried running your SQL query on the database correctly to make sure it actually works?