On 7-10-2011 11:12, tomc7777777 wrote:

>> There's no way subselects can be materialized, at least doing ..
>
> My use of the term 'materialized' may have been misunderstood, it was meant to relate to whether/how the sub-select row is retrieved and compared when * vs 1 are used.
>
> I've a copy of Celko's 'SQL for Smarties' and he outlines the theoretical way this happens but I think says it would never happen this way in reality and is implementation-specific. If someone with intimate knowledge of the FB source (and ideally a humble disposition) could show a briefly summary of the actual steps in resolving the SQL above then that would be much appreciated.

You are reversing the argument. First the row needs to be found based on
the WHERE clause (using indices and/or natural scan of all the rows),
and then the columns specified in the select are returned (be it a
specific list or *). Using the reverse would be absurd, because then the
selection of rows would depend on the columns you want to be returned
from a row.
--
Mark Rotteveel