Testing for IS NOT NULL with left join tables

Question

Dear Experts,
The query is showing the NULL rows in the query below....
Any ideas, advice please? tx, sandra
This is the sql inspector:
SELECT O100321.FULL_NAME_LFMI, O100321.ID, O100404.ID, O100321.ID_SOURCE
, O100404.NAME, O100321.PERSON_UID, O100404.PERSON_UID, O100404.VISA_TYPE
FROM ODSMGR.PERSON O100321
, ODSMGR.VISA O100404
WHERE ( ( O100321.PERSON_UID = O100404.PERSON_UID(+) ) ) AND ( O100404.VISA_TYPE(+) IS NOT NULL )

Answer 1

Hi Everyone,
I am understanding alot of what Michael and Rod wrote.... I am just puzzled over the following:
the query below is left joining the STUDENT table to
HOLD table.
The HOLD table - contains rows for students who have holds on their record.
a student can have more than one hold (health, HIPAA, basic life saving course)
BUT, for this query: I'm only interested that a hold exists, so I'm choosing MAX on hold desc.
Selecting a MAX, helps me, bec. it reduces my join to a 1 to 1 relationship, instead of
1 to many relationship.
Before I posted this thread at all, the LEFT JOIN below testing for IS NOT NULL worked w/o
me having to code IS NOT NULL twice....
Is that because, what's happening "behind the scenes" is that a temporary table containing all max rows is being
created, for which Discoverer has no predefined join instructions, so it's letting me do a LEFT JOIN and have
the IS NOT NULL condition.
I would so appreciate clarification. I have a meeting on Tues, for which I have to explain LEFT JOINS to the user
and how they should create a query. I need to come up with rules.
If I feel "clear", I asked my boss to buy Camtasia videocast software to create a training clip for user to follow.
Also, if any Banner user would like me to email the DIS query to run on their machine, I would be glad to do so.
thx sooo much, Sandra
SELECT O100384.ACADEMIC_PERIOD, O100255.ID, O100384.ID, O100255.NAME, O100384.NAME, O100255.PERSON_UID, O100384.PERSON_UID, MAX(O100255.HOLD_DESC)
FROM ODSMGR.HOLD O100255, ODSMGR.STUDENT O100384
WHERE ( ( O100384.PERSON_UID = O100255.PERSON_UID(+) ) ) AND ( O100384.ACADEMIC_PERIOD = '200820' )
GROUP BY O100384.ACADEMIC_PERIOD, O100255.ID, O100384.ID, O100255.NAME, O100384.NAME, O100255.PERSON_UID, O100384.PERSON_UID
HAVING ( ( MAX(O100255.HOLD_DESC(+)) ) IS NOT NULL )
ORDER BY O100384.NAME ASC