Let R be a relation with attributes ABCD. Consider the SQL conjunctive query
select x.B, z.D
from R x, R y, R z where x.A = z.D and y.C = 0 and x.B = y.B and z.B = 5 and z.C = y.C
(i) Construct the pattern corresponding to the query.
(ii) Is the pattern constructed in (i) minimal? (Explain)
(ii) Minimize the pattern in (i) knowing that the query is only applied to databases satisfying the FD’s
A → D, CD → B, C → A.
Show the intermediate steps.
(iii) Construct from the minimized pattern a corresponding minimized SQL query.
求大佬 解題帶解釋， 感激無盡.
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