![]() You would rewrite W with a better key (c,b), since c->a means that c is a better key than a. After that the normalisation is straightforward, and the result is that shown here. ![]() This set of relations solves nothing, and does not change the fact that W is still not in BCNF. ![]() This set of relations are actually valid when considered seperately, but the resulting query is suboptimal and could result in spurious values (if 'a' contained duplicate values). ![]() You cannot delete a directly from the composite key of W, as this would be an illegal operation. You must have 'a' in the key, either directly or indirectly. Note that as c gives a, you could substitute the attribute c every time you use a in a key. ![]() You would rewrite W with a better key (c,b), since c->a means that c is a better key than a. After that the normalisation is straightforward. If the relation W was normalised to BCNF, select the best resulting relationsof that process. W(a,b,c,d,e) c -> a
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