Joe Celko's SQL for Smarties, 3rd Edition

16.2. Quantifiers and Missing Data

The quantified predicates are used with subquery expressions to compare a single value to those of the subquery, and take the general form <value expression> <comp op> <quantifier> <subquery>. The predicate "<value expression> <comp op> [ANY|SOME] <table expression>" is equivalent to taking each row, s, (assume that they are numbered from 1 to n) of <table expression> and testing "<value expression> <comp op> s" with ORs between the expanded expressions:

((<value expression> <comp op> s1)
OR (<value expression> <comp op> s2)
      ...
OR (<value expression> <comp op> sn))

When you get a single TRUE result, the whole predicate is TRUE.

As long as <table expression> has cardinality greater than zero and one non-