On Wed, Aug 14, 2019 at 4:50 AM Dave via Python-list <python-list@python.org> wrote: > Some of the tables are related. For example: > > Hiking_Table Trails_Table Joining_Table > ----------------- -------------------- ----------------- > hike_id PK trail_id PK hike_id FK > hike_date TEXT trail_name TEXT trail_id FK > hike_destination TEXT trail_rating REAL > hike_rating REAL trail_comments TEXT > hike_comments TEXT > > So far, so good. I know how to create the tables. What I am struggling > with is how do I insert data into the joining table or don"t I? If so, > do I need to query the other two tables to get the auto-number ID's? > Some things I have read suggest that the joining table just contains > references, so there is no actual insert. A pointer to information how > to do this would be appreciated. As for queries, I think I use joins, > but a pointer on how to do this would also be appreciated.
The joining table is a real thing, and will have real inserts. It might be easier to think of this as two separate one-to-many relationships; for the sake of demonstration, I'm going to add another column to your joining table. hike_sections ==> hike_id references hikes, trail_id references trails, companion_name You've decided to have someone with you for some sections of your hike. As such, what we have is a number of "mini-hikes" that make up a single hike (that's a one-to-many relationship between hikes and sections), and also a single trail can be a section of any number of hikes (so, another one-to-many relationship between trails and sections). For any given section, there is exactly one companion. Does this make the many-to-many relationship a bit easier to understand? It'll work exactly the same way even if you have no ancillary information in that joining table. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
