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calikidd Posts: 41	Posted 03:02 Oct 07, 2010 \| For question 3.23, 1. Are these the correct entities: People, Cars, Policy, Accidents ? 2. Would it make sense do have a Coverage entity? Last edited by calikidd at 03:03 Oct 07, 2010.
ashasabeer Posts: 55	Posted 07:39 Oct 07, 2010 \| I do Have a question. Can we add new attributes for an entities which are not mentioned in the question? For Example : Can we add Accident_Id (which is not mentioned in the question) Attribute for an Accidents Entity? Thanks Asha
cysun Posts: 2935	Posted 08:18 Oct 07, 2010 \| ashasabeer wrote: I do Have a question. Can we add new attributes for an entities which are not mentioned in the question? For Example : Can we add Accident_Id (which is not mentioned in the question) Attribute for an Accidents Entity? Thanks Asha Yes.
calikidd Posts: 41	Posted 19:34 Oct 09, 2010 \| Does an entity have to have a key?
cysun Posts: 2935	Posted 19:48 Oct 09, 2010 \| calikidd wrote: Does an entity have to have a key? Yes, each entity set must have a key.
calikidd Posts: 41	Posted 20:40 Oct 09, 2010 \| cysun wrote: calikidd wrote: Does an entity have to have a key? Yes, each entity set must have a key. ok, but a primary key for 1 table can't be a primary key for another right? But it can be a foreign key for another table? Last edited by calikidd at 03:23 Oct 10, 2010.
calikidd Posts: 41	Posted 04:00 Oct 12, 2010 \| For 3.24, do we split the problem. In other words, do we make 2 separate ER diagrams?
cysun Posts: 2935	Posted 07:41 Oct 12, 2010 \| calikidd wrote: cysun wrote: calikidd wrote: Does an entity have to have a key? Yes, each entity set must have a key. ok, but a primary key for 1 table can't be a primary key for another right? But it can be a foreign key for another table? Yes.
cysun Posts: 2935	Posted 07:43 Oct 12, 2010 \| calikidd wrote: For 3.24, do we split the problem. In other words, do we make 2 separate ER diagrams? It's still one ER diagram.
calikidd Posts: 41	Posted 19:55 Oct 13, 2010 \| Does a table have to be either 3NF or BCNF? Can it be neither?
cysun Posts: 2935	Posted 22:12 Oct 13, 2010 \| calikidd wrote: Does a table have to be either 3NF or BCNF? Can it be neither? Of course it can, like the table shown in the first slide of the Normalization lecture notes. But if a table is not 3NF/BCNF, chances are it's not designed correctly (again, like the table shown in the lecture notes).
dedward Posts: 22	Posted 00:19 Oct 10, 2012 \| For Problem 3.24 Video-Rental Store, the third bullet specifies that customers can rate movies. Is the customer rating the same entity as the movie rating mentioned in the first bullet?
cysun Posts: 2935	Posted 07:48 Oct 10, 2012 \| dedward wrote: For Problem 3.24 Video-Rental Store, the third bullet specifies that customers can rate movies. Is the customer rating the same entity as the movie rating mentioned in the first bullet? No. Movie ratings are G, PG, PG13, R, and so on. A customer's rating of a movie is a number (usually between 1-5 or 1-10).