I am probably missing something very obvious, but after looking and
looking I just don't see it.

I have the following query:

SELECT DISTINCT A.AMT, A.CONTRACT
FROM ATABLE A, BTABLE B, CTABLE C
WHERE
( (B.X = '011170' AND B.Y = A.W)
OR
(C.M = A.Z AND C.N = A.T)
)
AND A.FYEAR = '2008'
AND A.FPRNO='3'

This yields an empty set.
However, if I remove the OR part and just have:

SELECT DISTINCT A.AMT, A.CONTRACT
FROM ATABLE A, BTABLE B
WHERE
( (B.X = '011170' AND B.Y = A.W)
)
AND A.FYEAR = '2008'
AND A.FPRNO='3'

Then it returns data.

Since (B.X = '011170' AND B.Y = A.W) is true and
(C.M = A.Z AND C.N = A.T) is false, shouldn't the compound statement in
the parenthesis in the first one, separated by an OR, yields true, and
so should yield data? It is acting as if (true or false) ===> false
rather than true.

You not only removed the OR, you also removed the join to table C.
A join with an empty table C won't return any data regardless of
the WHERE clause.

I have to wonder if you really mean 'OR' (as distinguished from
'AND'). Assuming there is one rows from the join of A and B that
satisfies:

B.X = '011170' and B.Y = A.W and A.FYEAR = '2008' and A.FPRNO='3'

and there are one million rows in table C, regardless of contents,
you're going to get one million rows returned.

If table C is empty, there are no records in the join, so the WHERE
clause is never evaluated.

You not only removed the OR, you also removed the join to table C.
A join with an empty table C won't return any data regardless of
the WHERE clause.

I have to wonder if you really mean 'OR' (as distinguished from
'AND'). Assuming there is one rows from the join of A and B that
satisfies:

B.X = '011170' and B.Y = A.W and A.FYEAR = '2008' and A.FPRNO='3'

and there are one million rows in table C, regardless of contents,
you're going to get one million rows returned.

If table C is empty, there are no records in the join, so the WHERE
clause is never evaluated.

You not only removed the OR, you also removed the join to table C.
A join with an empty table C won't return any data regardless of
the WHERE clause.

I have to wonder if you really mean 'OR' (as distinguished from
'AND'). Assuming there is one rows from the join of A and B that
satisfies:

B.X = '011170' and B.Y = A.W and A.FYEAR = '2008' and A.FPRNO='3'

and there are one million rows in table C, regardless of contents,
you're going to get one million rows returned.

If table C is empty, there are no records in the join, so the WHERE
clause is never evaluated.

You not only removed the OR, you also removed the join to table C.
A join with an empty table C won't return any data regardless of
the WHERE clause.

I have to wonder if you really mean 'OR' (as distinguished from
'AND'). Assuming there is one rows from the join of A and B that
satisfies:

B.X = '011170' and B.Y = A.W and A.FYEAR = '2008' and A.FPRNO='3'

and there are one million rows in table C, regardless of contents,
you're going to get one million rows returned.

If table C is empty, there are no records in the join, so the WHERE
clause is never evaluated.

Gordon Burditt wrote:

That is the answer.

Gordon Burditt wrote:

That is the answer.

Gordon Burditt wrote:

That is the answer.

Gordon Burditt wrote:

That is the answer.