No, marking as date table creates no relationships, nor vice versa. What marking as date table does is validates that the date field specified fully meets this list of criteria:
- contains unique values
- contains no null values
- contains contiguous date values (from beginning to end)
- if it is a Date/Time data type, it has the same timestamp across each value
Beyond specifying the proper relationship(s) between the date table and other table(s) in the model, the marking step is critical to maximize time intelligence capabilities. It will get rid of the automatic date hierarchies created by Power BI (which many people, me included, find cumbersome and difficult to work with), and certain time intelligence functions expect to find in their first parameter a date field that meets the above validation criteria.
I hope this helps clarify things.
- Brian
BTW - welcome to the forum!