Thanks for the nice explanation. At 10:30 around, it was mentioned that ship_id dets captain_id (this assumes a ship is associated with a captain, else a ship can have mul captains). In that case captain_id also should det ship_id (as a ship always associated with captain), but at 10:38 its given that captain_id does not det ship_id. Some pls clarify. Thank you....
You could argue that, but in that case you would have an equivalent dependency. Therefore, you must get rid of a dependency. In that case, you would end up with the same dependencies or you would have the alternate dependencies as you suggested.
Hi, here (10:17) just like we argued that Captain_id cannot determine the ship_id, cuz one ship can have multiple captains assigned to it, why can't we think that ship_id cannot determine the captain_id or captain_name? (09:42) I'm kinda stuck in that point. I got the answer as "ship_id--->shipname"; indicating it's only the shipname that can be identified by ship_id. can u plss explain?
The reason why I say that a ship_id can't determine multiple captains is because we have one captain at a moment in time and the others aren't captains but first mate, etc. If we had another captain of the ship, we would replace the existing captain with the new captain and there would still be only one captain of the ship. Now, if your model says that you can have multiple captains of a ship at the same time, then your logic might work too. What is important is that you figure out all the one-to-one functional dependencies and then model based on what you discovered.
