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HAVING clause check?
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08/05/2008 14:45:21
 
 
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Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Titre:
HAVING clause check?
Versions des environnements
Visual FoxPro:
VFP 9 SP1
OS:
Windows XP SP2
Network:
Windows 2003 Server
Database:
Visual FoxPro
Divers
Thread ID:
01315930
Message ID:
01315930
Vues:
63
Hi all,

Usually I use the "HAVING" clause in a SELECT statement to limit result rows in a situation where I am doing a GROUP BY at the same time (like a count using a GROUP BY).

Is it legit - i.e. will I get correct results - to use filter conditions in the HAVING clause to avoid repeating a filter condition in a UNION? i.e. I have a 3 way UNION each of which has a couple of unique conditions but then all 3 of them have 3 more conditions. Instead of repeating these last 3 conditions 3 times, I thought maybe I could put them in as a "HAVING" as I think I remember reading that that works like a WHERE clause and is processed after the UNION is done. BTW, the unique conditions are complex enough I don't want to try to code a complicated set of conditions joined by two "OR"s. By doing it as a UNION, it is much more readable.

Just want to confirm. Here is the example:
SELECT ;
   File.* ;
   FROM File ;
   WHERE <unique conditions> ;
UNION SELECT ;
   File.* ;
   FROM File ;
   WHERE <more unique conditions> ;
UNION SELECT ;
   File.* ;
   FROM Files ;
   WHERE <more unique conditions> ;
HAVING ;
   < 3 conditions common to the above)
INTO CURSOR x
Thanks,
Albert
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