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______ operation preserves those tuples that would be lost in____

(a) Natural join, Outer join

(b) Outer join, Natural join

(c) Left Outer Join, Right Outer Join

(d) Left Outer Join, Natural Join
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Always in outer join, the non-matching tuples are also preserved.

But whereas in natural join only matching tuples are considered.
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(b) is the correct answer.

Outer join (Full outer join) preserves those tuples that would be lost in natural join.

Consider two relations

Relation 1:

A B
1 a
2 b
3 c

 

Relation 2:

B C
a 4
c 6

 

A ⋈ B

A B C
1 a 4
3 c 6

 

Full Outer JoinB

A B C
1 a 4
2 b NULL
3 c 6

 

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