An IN predicate compares a value with another value or a
    collection of values.

  in-predicate =

  --> value-expr +--------+-> IN +-> value-expr ------------------+->
                 +-> NOT -+      +-> ( -++-> value-expr  --++-> ) +
                                        |+-> select-expr --+|
                                        +---------- , <-----+

    All forms of the IN predicates can be represented using other
    conditional operators.

    o  value-expr IN value-expr

       is the same as

       value-expr IN (value-expr)

       which is the same as the basic predicate

       value-expr = value-expr

       (as long as the value expression on the right is not a host
       structure that expands to more than one parameter)

    o  value-expr IN (value-expr1, value-expr2, value-expr3)

       is the same as the complex predicate

       value-expr = value-expr1
       OR
       value-expr = value-expr2
       OR
       value-expr = value-expr3

       (in this case, any of the value expressions on the right can
       be a host structure that expands to more than one parameter)

    o  value-expr IN (col-select-expr1, val-expr2, col-select-expr3)

       is the same as the quantified predicate

       value-expr = ANY (col-select-expr1)
       OR
       value-expr = val-expr2
       OR
       value-expr = ANY (col-select-expr3)

       (in this case, any of the value expressions on the right can
       be a host structure that expands to more than one parameter)