Re: SQL Union Join?

Never heard of a "UNION JOIN"

Googling for it turned up a page that said UNION JOIN was a FULL OUTER
JOIN with matches removed, which I believe is what Elvis called a FULL
EXCEPTION JOIN. I don't see that as a standard name, but it makes
more sense than UNION JOIN I think.

Charles



On Thu, Mar 26, 2009 at 11:26 AM, Michael Ryan <michaelrtr@xxxxxxxxx> wrote:

Thanks Charles. Do you know if a UNION JOIN (which I don't think is
supported on V5R4) that same as a FULL OUTER JOIN?

On Thu, Mar 26, 2009 at 11:15 AM, Charles Wilt <charles.wilt@xxxxxxxxx>wrote:

Michael,

Basically, for detecting mismatches across two files what you want is
called a FULL OUTER JOIN.

Unfortunately, the i doesn't support FULL OUTER JOINs until 6.1.

However, you can get the same results as a FULL OUTER JOIN by using a
UNION of the results from LEFT OUTER and RIGHT EXCEPTION.


http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/sqlp/rbafysimulatefoj.htm
 (note IBM example in manual uses flips the table order and uses
EXCEPTION join, it's kinda confusing :)

select * from tableA left outer join tableB using (SKU,name, Category)
UNION ALL
select * from tableA right exception join tableB using (SKU,name, Category)

This would give you all rows from both tables:
SKU   NAME        CATEGORY  SKU   NAME        CATEGORY
123   NAME1         1,001      -  -                  -
456   NAME2         1,002   456   NAME2         1,002
123   NAME1         1,002   123   NAME1         1,002
789   NAME3         1,004      -  -                  -
  -  -                  -    1   SOMETHING     1,002
  -  -                  -  123   NAME1         1,003

Since you only want mismatching, add a where:
select * from tableA A left outer join tableB B using (SKU,name, Category)
where b.sku is null
UNION ALL
select * from tableA A right exception join tableB B using (SKU,name,
Category)
where a.sku is null

which gives you:
SKU   NAME        CATEGORY  SKU   NAME        CATEGORY
123   NAME1         1,001      -  -                  -
789   NAME3         1,004      -  -                  -
  -  -                  -    1   SOMETHING     1,002
  -  -                  -  123   NAME1         1,003


But it seems as if you don't want mismatches from both files, instead
what you want are only records from tableB that have a mismatched
category compared to tableA.

select * from tableB B
where exists (select 1 from tableA A
             where b.sku = a.sku
               and b.name = a.name
               and b.category <> a.category)
 and not exists (select 1 from tableA A
                where b.sku = a.sku
                  and b.name = a.name
                  and b.category = a.category)

HTH,
Charles



On Thu, Mar 26, 2009 at 9:30 AM, Michael Ryan <michaelrtr@xxxxxxxxx>
wrote:

If I have two tables (TABLEA, TABLEB) that have the same format, and I

want

to retrieve all the rows where a combination of two columns don't match,
would that be a union join? If so, how is that specified? Here's what I
have:

TABLEA and TABLE have the format of SKU, name and category. A SKU could
exist in multiple categories.

TABLEA
123, NAME1, 1001
456, NAME2, 1002
123, NAME1, 1002
789, NAME3, 1004

TABLEB
001, SOMETHING, 1002
123, NAME1, 1003
456, NAME2, 1002
123, NAME1, 1002

I want to retrieve 123, NAME1, 1003 because that's the one that has a
different category. I don't want to retrieve SKU 456, 789, or 001.
Hmmm...maybe I need to match on SKU with a subselect for that SKU not

having

that category?

Thanks!
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