Set-Difference Operations in RDBMS
* The Set-Difference operation , denoted by "-" allows
us to find the tuples that are in one relation but not in another .
* The expression , ( r - s ) produces a relation containing
those tuples in r but not in s .
* One can find all the customers of the bank who have an account
but not a loan by writing in the below manner :
* In the case of the Union Operation , one must ensure that the
set differences are taken between compatible relations .
* For a set-difference operation where "r-s" to be valid , one requires that the relations r and s be of the same arity , and that the domains of the ith attribute of r and the ith attribute of s should be the same .
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