RE: Avoiding Duplicates and Transitive Operations

Wow, I guess we all have or not so bright moments.

Ian MacGregor
Stanford Linear Accelerator Center
ian_at_slac.stanford.edu

-----Original Message-----
Sent: Friday, July 27, 2001 5:36 PM
To: Multiple recipients of list ORACLE-L

...

>What I want to know is if
>
>SQL> SELECT C1, C2 FROM ian.TEST1
> 2 WHERE EXISTS (SELECT C1 FROM ian.TEST2)
>
>
>undergoes a transitive operation to
>
> SELECT C1, C2 FROM ian.TEST1
> 2 WHERE EXISTS (SELECT C1 FROM ian.TEST2
> where test1.c1 = test2.c1)
>
>/
>------------------------------------------------------------------------------------------------------------------------

Of course not, why would it do that? All you asked for was the records from TEST1 as long as there exist ANY records in TEST2, and that's what you got. If you add more records to TEST1, you would see that you have established no links between the tables. If you want the second statement, you have to ask for it.

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Author: MacGregor, Ian A.
  INET: ian_at_SLAC.Stanford.EDU

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