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