Joe Celko (12/17/2008)
The calendar date is the natural key, so the magically vague "id" is not needed. The table is not normalized to 1NF -- you have data and metadata in it. What do the NULLs mean?
The reason that I added the date_id column is to allow the dimension to be referenced by a 4-byte value instead of an 8 byte value if the application calls for linking data to a coordinate.