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@setspace.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