On 23/10/12 11:21, Kjell Rilbe wrote:
> Den 2012-10-23 10:32 skrev Frank såhär:
>> select R1.RDB$RELATION_NAME
>> from RDB$RELATION_FIELDS F1
>> join RDB$RELATIONS R1 on F1.RDB$RELATION_NAME = R1.RDB$RELATION_NAME
>> where F1.RDB$FIELD_NAME ='EMP_NO' and
>> (not exists(select R2.RDB$RELATION_NAME
>> from RDB$RELATION_FIELDS F2
>> join RDB$RELATIONS R2 on F2.RDB$RELATION_NAME=R1.RDB$RELATION_NAME
>> where F2.RDB$FIELD_NAME ='PHONE_EXT'));
> Although I can't see why it would give the indicated error, the query
> seems utterly pointless. R2 and F2 are not correlated and so the
> subquery will return all F2 records paired with all R2 records. I think
> it's a typo and that the subquery's join condition should refer to R2,
> not R1.
No, this query returns all tables from employee.fdb
that contain a field EMP_NO, but not PHONE_EXT.
This is of course just a simplified example to show the 'feature' we
stumbled upon.
Frank
--
"Fascinating creatures, phoenixes, they can carry immensely heavy loads,
their tears have healing powers and they make highly faithful pets."
- J.K. Rowling
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