Question

I am trying to get the default value for a column but unfortunately I get nothing.
Here is my code:

'ColumnName is the Column Name in question
'BaseTableName is the Table Name
   Dim myCon As New OracleConnection
   myCon.ConnectionString = gApp.ConnectString
   myCon.Open()
   Dim myCmd As New OracleCommand
   myCmd.Connection = myCon
   myCmd.CommandType = CommandType.Text
   myCmd.CommandText = "select data_default " & _
          "from all_tab_columns " & _
          "where table_name='" & BaseTableName & "' " & _
          "and column_name='" & ColumnName & "'"
   Dim dr As OracleDataReader
   dr = myCmd.ExecuteReader
   dr.Read()
   Dim val = dr.GetValue(0).ToString

   '  Dim val = myCmd.ExecuteScalar 'I tried also with executeScalar but it was the same

   myCon.Close()

When I execute the same string in oracle it returns a Long and inside the long is the default value

How can I get the original value inside the long?

Answer 1

Assuming the problem is because your environment doesn’t support LONGs, you can create a function to convert the value to a VARCHAR2 first. For example:

create table test1(a number default 0);

create or replace function get_data_default(
    p_owner varchar2,
    p_table_name varchar2,
    p_column_name varchar2
) return varchar2 authid current_user is
    v_data_default varchar2(4000);
begin
    select data_default
    into v_data_default
    from all_tab_columns
    where owner = p_owner
        and table_name = p_table_name
        and column_name = p_column_name;

    return v_data_default;
end;
/

select get_data_default(USER, 'TEST1', 'A') from dual;

0

If you have this problem with other columns, you can make the function more generic, or you can look into a utility to convert all the dictionary LONGs to CLOBs. The Dictionary Long Application can do this, although it can get very complicated.