Indeed.
__________________________________________________________________________________
Mike Blackwell | Technical Analyst, Distribution Services/Rollout
Management | RR Donnelley
1750 Wallace Ave | St Charles, IL 60174-3401
Office: 630.313.7818
Mike.Blackwell@rrd.com
http://www.rrdonnelley.com
On Fri, Apr 13, 2012 at 13:34, Scott Marlowe <scott.marlowe@gmail.com> wrote:
> On Fri, Apr 13, 2012 at 11:59 AM, Jack Christensen
> <jackc@hylesanderson.edu> wrote:
>> On 4/13/2012 11:39 AM, Mike Blackwell wrote:
>>>
>>> Could someone please explain to me why the following select does not
>>> result in a syntax error? (9.0.3)
>>>
>>> begin;
>>>
>>> create table x( c1 integer , c2 integer);
>>> create table y( c3 integer, c4 integer);
>>>
>>> select * from x where c2 in ( select c2 from y where c4 = 2 );
>>>
>>>
>>> rollback;
>>>
>>> Mike
>>>
>> Your subquery is correlated with the outer query. So the c2 in the subquery
>> is referring to table x.
>
> This is a good example of why one should always use a table alias
> prefix when using subqueries.
>
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