How to get table name of a column from SqlDataReader

I don't know if this information is available. In particular, not all columns of a result set come from a table. From a relational point of view, tables and resultsets are the same thing.

You can use SqlDataReader.GetSchemaTable to get table information but you have to set CommandBehavior to KeyInfo, you do that in the ExecuteReader call:

reader = cmd.ExecuteReader(CommandBehavior.KeyInfo);

This unanswered question on stackoverflow uses SqlDataReader.GetSchemaTable to get the table name. Their problem is that it returns the actual table name rather than the alias that the table has. Not sure if this works with your sql but figured I'd let you know just in case.

reader = cmd.ExecuteReader();
reader.GetSchemaTable().Rows[0]["BaseTableName"];