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ORA-01417:  a table may be outer joined to at most one other table tips

Oracle Error Tips by Donald Burleson(S. Karam)


The Oracle docs note this on the ora-01417 error:

ORA-01417: a table may be outer joined to at most one other table
Cause: a.b (+) = b.b and a.c (+) = c.c is not allowed
Action: Check that this is really what you want, then join b and c first in a view. Forums contains a thread dealing with the necessity to resolve an ORA-01417 issue:

Question :

cchiara asked:

I have this statement in a view and want to put outer join on the weakness table.
How can I resolve this error ORA-01417


DaPi04 advised:

I would strongly suggest you draw a data model (entity-relationship or whatever) for these tables. I suspect you have started off on the wrong foot and a diagram should help you clarify the situation. Then start to put it together one table at a time.

(Check that you have the (+) on the correct side of the conditions. Some of your conditions look suspect to me, though it's hard to tell without knowing your application.)
I think there is something fundamentally wrong. The only relationship between poam and milestone I can see is this:p.poam_id = w.poam_id (+) AND
w.weakness_id (+) = m.weakness_id Which, if it were permitted and meant something, would:

EITHER produce a Cartesian product - all rows of poam would match all rows of milestone via the NULL rows of weakness in the outer join (allowing NULL=NULL to be true)

OR lose all the rows where there are none corresponding in weakness (allowing NULL=NULL to be false), in which case you don't have an outer join.

What I have just written boarders on the incomprehensible - you need a picture. I say again: LOOK TO THE DATA MODEL.



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