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Database Languages eXercises #1

The Relational Model - Solutions


A.
1. and 2.
table (a) is NOT relationally acceptable - the medals column contains 
repeating groups.  table (b) is fine relationally, but could be difficult 
to use for things like medal tallies.  table (c) is the preferred one 
for most transactions.

B.
table (a) states that the tigers have scored NO wins, whereas table(b) 
states that the number of wins for the tigers is un-recorded

C.
(a) Name, assuming name uniquely identifies a person
(b) Name+Subject (a person can study many subjects, a subject can be studied by many students)
(c) Language (is there a choice?)
(d) Language (as a language is either recursive or not)
(e) Manufacturer + Model + Year
(f) Day + Subject + Period

D.
1. if ties are allowed, then School+Event could be a key if a school is allowed 
to enter maximum one entrant per event
2. if ties are NOT allowed, then School = Event could be a key for the same 
reasons as above, in addition, Place + Event would be a key.

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