4. a) Suppose relation R(a,b.c) has the following tuples: (1,1.3), (1,2,3), (2,1

Question

4. a) Suppose relation R(a,b.c) has the following tuples: (1,1.3), (1,2,3), (2,1,4), (2,3,5), (2,4,1), (3,2,4), and (3,3,6). Define the view Vby: CREATE VIEW V AS SELECT a+b AS d, c FROM R; What is the result of the query: SELECT d, SUM(c) FROM V GROUP BY d HAVING COUNT1; (5) b) The table Arc(x.y) currently has the following tuples (note there are duplicates): (1,2), (1,2), (2,3), (3,4), (3,4), (4,1), (4,1), (4,1), (4,2). Compute the result of the query: SELECT al.x, a2.y, COUNT(*) FROM Arc a1, Arc a2 WHERE al.y = a2.x GROUP BY al.x, a2.y;

Explanation / Answer

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R(a, b, c)

1 1 3

1 2 3

2 1 4

2 3 5

2 4 1

3 2 4

3 3 6

V(d,c)

2 3

3 3

3 4

5 5

6 1

5 4

6 6

GROUP BY d

d -> count(*)

2 -> 1

3 -> 2

5 -> 2

6 -> 2

result:

3 7

5 9

6 7

2)

Arc(x,y)

1 2

1 2

2 3

3 4

4 1

4 1

4 1

4 2

SELECT * FROM Arc1 a1, Arc a2 WHERE a1.y = a2.x;

1 2 2 3

1 2 2 3

2 3 3 4

3 4 4 1

3 4 4 1

3 4 4 1

3 4 4 2

4 1 1 2

4 1 1 2

4 1 1 2

4 1 1 2

4 1 1 2

4 1 1 2

4 2 2 3

GROUP BY a1.x, a2.y

1 2 2 3

2 3 3 4

3 4 4 1

3 4 4 2

4 1 1 2

4 2 2 3

result:

1 3 2

2 4 1

3 1 3

3 2 1

4 2 6

4 3 1

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