A true constraint is owned by a single table but can affect multiple columns. For instance, I can have a PRIMARY KEY constriant for column1 and column2:

CONSTRAINT name PRIMARY KEY (column1, column2)

But a default constraint is applicable to only one column.

I haven't been able to determine an easy way to identify DEFAULT constraints. It appears that none of the INFORMATION_SCHEMA views reveals that information, and SQL-DMO doesn't either. I think you'll either have to hit the system tables directly or use sp_helpconstraints.

-Mike