Обсуждение: IN with arrays

I'm wondering why a IN b isn't equivalent to a = ANY b for arrays, as it 
is for subqueries.

That is, why can't you write

SELECT 1 IN ( ARRAY[1, 2, 3] );

when you can write

SELECT 1 = ANY ( ARRAY[1, 2, 3] );

?

I'm guessing that there is a semantic inconsistency between these 
expressions, as the first one considers what is in parentheses as a 
list, the second one as a single expression.  That would be very bad.

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/

Peter Eisentraut <peter_e@gmx.net> writes:
> That is, why can't you write
> SELECT 1 IN ( ARRAY[1, 2, 3] );
> when you can write
> SELECT 1 = ANY ( ARRAY[1, 2, 3] );
> ?

The two syntaxes are in fact *not* equivalent according to SQL92.
= ANY derives from
        <quantified comparison predicate> ::=             <row value constructor> <comp op> <quantifier> <table
subquery>
        <quantifier> ::= <all> | <some>
        <all> ::= ALL
        <some> ::= SOME | ANY

(notice the RHS *must* be a <table subquery>) whereas IN comes from
        <in predicate> ::=             <row value constructor>               [ NOT ] IN <in predicate value>
        <in predicate value> ::=               <table subquery>             | <left paren> <in value list> <right
paren>
        <in value list> ::=             <value expression> { <comma> <value expression> }...

The form "expr = ANY (non-query-expr)" is therefore a spec extension,
which we are free to define as we wish, and we defined it to be a
scalar-vs-array-elements comparison.  But I don't see any way that we
can interpret "expr IN (other-expr)" as anything except a variant
spelling for a simple equality test.
        regards, tom lane