Re: question about join

Osvaldo Kussama ha scritto:
>>  To further explain, the following query selects both the rows from the join
>> where id_ref_first_tab has the desired value and default_value = true, while
>> I want to select the row corresponding to default_value = true only in case
>> no row corresponding to id_ref_first_tab exists.
>>
>>  select * from second_table join third_table on second_table.id =
>> third_table.id_ref_second_tab where id_ref_first_tab = 1 or default_value =
>> true;
>>
>>  I hope I've been clear enough...
>
> Try:
> select * from second_table join third_table on second_table.id =
> third_table.id_ref_second_tab
> where id_ref_first_tab = 1 or (id_ref_first_tab <> 1 and default_value = true);

it's not what I want, because it can return two rows, while I want only
one row back, checking the first condition and optionally the second one
only if the first one is not matched.

I don't know if it is possible, but if it could, it would be great.

--
Non c'e' piu' forza nella normalita', c'e' solo monotonia.