* gregory lefebvre
> I try to translate in MySQL language a problem which I mean is a UML
> partition constraint.
>
>
> I explain:
>
> There is a table A binded with a table B.
> This table B is itself binded according to a B.P parameter:
> either to a table C
> either to a table D
> but never to both.
>
> I think one solution should be to do a first SELECT on B in order to
> determine B.P. Thus I should do again a SELECT on the 3 tables according
> to the B.P in the WHERE clause.
>
> BUT I would like to do a one time SELECT on A->B->C or A->B->D.
> I cannot translate this constraint in SQL for MySQL.
>
> Could someone who unsderstood this incomprehensible description
> help me. ;o)
Have you tried something like this:
SELECT A.*,B.*,IF(B.BP='C',C.data,D.data) as "C or D"
FROM A
LEFT JOIN B ON
B.AID=A.AID
LEFT JOIN C ON
C.BID=B.BID AND B.BP = 'C'
LEFT JOIN D ON
D.BID=B.BID AND B.BP = 'D'
WHERE ...
I think it should solve your problem.
HTH,
--
Roger
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