How to get column default value define on table?

Question

Hi,
I am trying to get a table column default value with no success. I am using the Oracle Data Provider for .NET 10g Release 2 (10.2.0.2)
1). OracleConnection.GetSchema( "Columns", New System.String() {"<Owner>", "<Table_Name>"} returns everything BUT default value.
2). I tried querying oracle directly (sample below) but the default value comes back blank even though the column has one defined.
Dim oracleConnection As Oracle.DataAccess.Client.OracleConnection = factory.CreateConnection
Dim oracleCommand As New Oracle.DataAccess.Client.OracleCommand( _
"SELECT data_default FROM DBA_TAB_COLUMNS WHERE OWNER = 'TEST_SCHEMA' AND UPPER( TABLE_NAME ) = 'TEST' AND UPPER(COLUMN_NAM) = 'TESTCOL'")
oracleConnection.Open()
oracleCommand.Connection = oracleConnection
Dim oracleReader As Oracle.DataAccess.Client.OracleDataReader = oracleCommand.ExecuteReader
oracleReader.GetValue(0) 'This will return blank rather than default value for the column.
oracleReader.Read()
oracleReader.Close()
oracleConnection.Close()
Any help would be appreciated.
Thanks,
Rob Panosh
Advanced Software Designs

Answer 1

Hi Rob,
I just ran up a quick test and I can't duplicate the behavior you describe.
I created a simple table as "scott":
SQL> create table def_test(c varchar2(32) default 'hello, world');
Table created.In my simple test I used the following C# code:
NOTE: There is an error in this code if using ODP.NET (see my post below for details on this)
using System;
using System.Data;
using System.Data.OracleClient;
class Program
  static void Main(string[] args)
    string constr = "user id=scott;" +
                    "password=tiger;" +
                    "data source=orademo;" +
                    "pooling=false;" +
                    "enlist=false";
    OracleConnection con = new OracleConnection(constr);
    con.Open();
    OracleCommand cmd = con.CreateCommand();
    cmd.CommandText = "select   data_default " +
                      "from     all_tab_columns " +
                      "where    owner='SCOTT' " +
                      "and      table_name='DEF_TEST' " +
                      "and      column_name='C'";
    OracleDataReader dr = cmd.ExecuteReader();
    dr.Read();
    string defaultValue = (string) dr.GetValue(0);
    Console.WriteLine("Default value is: {0}", defaultValue);
    dr.Dispose();
    cmd.Dispose();
    con.Dispose();
}Since the GetValue method returns an "object" I cast the value to a string and got the correct result.
However, I don't have a 10.2 ODP.NET environment right now so I was using 11.1 for this.
In your real code I suspect that you assign "oracleReader.GetValue(0)" to something - when you say "blank" do you mean zero length or a space or something else?
Regards,
Mark
Edited by: Mark Williams on Jul 31, 2009 10:02 AM