the query
select COLUMN_DEFAULT
from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = @tableName
and COLUMN_NAME = @columnName
will return the default value specified for a column (null
if no default was defined)
Update:
The following query will also retrieve the constraint's name:
select
dc.name,
dc.definition
from sys.default_constraints dc
join sys.objects o
on o.object_id = dc.parent_object_id
join sys.columns c
on o.object_id = c.object_id
and c.column_id = dc.parent_column_id
where o.name = @tableName
and c.name = @columnName
If no rows are returned, then there's no default constraint defined on the column.