Re:

well, it seems to me that section 9.20.2 makes sense.
http://www.w3schools.com/sql/sql_in.asp
I am not sure that you can compare multiple columns such as in:

SELECT * FROM Persons WHERE LastName, FirstName IN (SELECT LastName,
FirstName FROM OtherPersons);

if this is what you mean, at least not using this method, which returns
an error.

d

Le 15/11/11 18:29, jmscott(at)setspace(dot)com a écrit :
> I would like clarification on the first paragraph of section 9.20.2 on
> the page at
>
> http://www.postgresql.org/docs/9.1/static/functions-subquery.html
>
> regarding the syntax of the 'expression in (subquery)' clause.
>
> What is meant by
>
> The right-hand side is a parenthesized subquery, which must return
> exactly one column.
>
> ? Appears to me that the subquery must only contain the same number of
> columns as the left hand side, not just 1 column.
>
> thanks-j
>
>