Database The completebook 2nd Edition Exercise 498 Under wh

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Database The completebook (2nd Edition)

Exercise 4.9.8:

Under what circumstances is a relationship its own inverse?
Hint : Think about the relationship as a set of pairs, as discussed in section 4.9.4

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Solution

ANSWER:   

A relationship R is it’s have inverse if and only if for each pair (a,b) in R, the pair (b,a) is too in R. from the terminology of set theory, the relation R be symmetric.