> Yes 'exists' works (though I never understood the advantage to the 'in'
operator).
Each has its advantages and weak points. Eg, in some DBMS, number of
entries of `in ( A1, ... AN )' has a pretty tight limit. Also, in PGSQL 7.0
having even fewer entries may cause `Tuple too big' error. Solution is to
replace explicit enumeration with comparisons. And so on.
`exists' is more `relational pure' on one hand, but is probably more
resource consuming.
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