The given query SELECT DISTINCT W, X FROM R, S Is guaranteed to be same as R, if R has no duplicates and ‘S’ is non-empty. Since, if R is having a duplicates, then the tuples selected by SELECT operation of the R and the given query will not be same also if ‘S’ is empty then the given query outputs null.
The given querySELECT DISTINCT W, XFROM R, SIs guaranteed to be same as R, if R has no duplicates and ‘S’ is non-empty.Since, if R is having a duplicates, then the tuples selected by SELECT operation of the R and the given query will not be same also if ‘S’ is empty then the given query outputs null.
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The given querySELECT DISTINCT W, XFROM R, SIs guaranteed to be same as R, if R has no duplicates and ‘S’ is non-empty.Since, if R is having a duplicates, then the tuples selected by SELECT operation of the R and the given query will not be same also if ‘S’ is empty then the given query outputs null.