Hey all,

I was a little confused by some of the questions on this exercise, read below:

• For Q3, there are two different ways to map a 1 to M relationship that are equally valid. Should we use the least possible number of tables?
• Can a editor edit many books?
• For 7-8 I followed the rule for any collections class that I know, but I noticed that we can mark more then one answer...Does that imply anything?

If anyone has any ideas about these questions let me know!

1. Yes (and I'm curious about the 2nd "equally valid" way).

2. Of course.

3. Don't worry about how many options you can choose - just choose the one (or ones) that you think is correct.

lmann2 wrote:

For Q1, I had ignored normalization and that pretty much answers my question.  However, my understanding for 1:N relationships is that you can create a third table that has the has the primary keys of both tables with the primary key of the new table being the primary key of the N side of the relationship. 

And in the same way you could create a fourth table, a fifth table, and so on and it would work, but I wouldn't consider it "equally valid" because it makes queries less efficient (due to an additional join) for no reason.

tonyg wrote:

For 7 and 8, do the options, "A foreign key column referencing the id column of the X table needs to be added to the Y table. ?"

suggest that a new column is created in addition to the existing columns, or simply that an existing column is modified to act as a foreign key?

The question is asking whether a new column needs to be created.