SQL Question

This is killing me because I'm certain I should know why this isn't working, but I can't seem to figure it out.  I have two queries in an Access database that I'm trying to join into 1 query that I can use as the data source for a report.  Here are the 2 queries:

Area  Machine   UnitOp  Mode  Occur  DT
----  -------   ------  ----  -----  -----
NULL  MachA     NULL    Leak  8      6.7
NULL  MachA     NULL    Can   4      0.28

Area  Machine   UT
----  -------   -------
NULL  MachA     331.497

The results should look like this:

Area  Machine   UnitOp  Mode  Occur  DT      UT
----  -------   ------  ----  -----  -----   -------
NULL  MachA     NULL    Leak  8      6.7     331.497
NULL  MachA     NULL    Can   4      0.28    331.497

However, when I run my query, either nothing from Query1 or Query2 shows, depending on which JOIN I use.  For example, originally my SQL looked like this:

SELECT Query1.*, Query2.UT
FROM Query1 LEFT JOIN Query2 ON (Query1.Machine = Query2.Machine) AND (Query1.Area = Query2.Area);

When I ran this, the data from Query1 showed up just fine, but the data from Query2 did not.  So, just to test, I switched to a RIGHT JOIN and the data from Query2 showed up just fine, but the data from Query1 didn't show up.  Does anyone see anything wrong with my queries or have a suggestion of how to better accomplish this?

Who is Participating?

Improve company productivity with a Business Account.Sign Up

Guy Hengel [angelIII / a3]Connect With a Mentor Billing EngineerCommented:
The problem is the NULL value:

SELECT Query1.*, Query2.UT
FROM Query1 JOIN Query2 ON (Query1.Machine = Query2.Machine) AND (IIF(Query1.Area IS NULL, 999,Query1.Area) = IIF(Query2.Area IS NULL, 999, Query2.Area));

Anthony PerkinsCommented:
I could be wrong, but I don't believe you can join fields that are Null.  In other words if the value is Null than it will not be included.

Guy Hengel [angelIII / a3]Billing EngineerCommented:
to explain:
-> returns false !!!!
This is true for other database systems also.
Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

i'm guessing the problem is here:
Query1.Area = Query2.Area

because you are doing where null = null which should probably be null is null so maybe modify query to be:

SELECT Query1.*, Query2.UT
FROM Query1 LEFT JOIN Query2 ON (Query1.Machine = Query2.Machine) AND ((Query1.Area is null AND Query2.Area is null) OR (Query1.Area = Query2.Area));

TimCotteeHead of Software ServicesCommented:
Select Query1.Area,Query1.Machine,QUery1.UnitOp,Query1.Mode,Query1.Occur,Query1.DT,Query2.UT From Query1 Inner Join Query2 On Query1.Machine = Query2.Machine And Query1.Area = Query2.Area


Select Query1.Area,Query1.Machine,QUery1.UnitOp,Query1.Mode,Query1.Occur,Query1.DT,UT = (Select Query2.UT From Query2 Where Query2.Machine = Query1.Machine And Query2.Area = Query1.Area) From Query1
SELECT Query1.*, Query2.UT
FROM Query1 LEFT JOIN Query2 ON (Query1.Machine = Query2.Machine)
Where Query1.Area Is Null and Query2.Area Is Null


SELECT Query1.*, Query2.UT
FROM Query1 LEFT JOIN Query2 ON (Query1.Machine = Query2.Machine) AND (Query1.Area = Query2.Area)
Where Query1.Area Is Not Null and Query2.Area Is Not Null
beercat2Author Commented:
Wow!  Thanks for all the quick replies.  Since I'm certain all of these would have worked, I'm just going to award the points to the first answer.

Thanks for all of your expertise!

Please verify answers before accepting them as valid.  Every suggested answer may NOT solve your problem.  Not all solutions are of equal value in all environments.  We experts only see the "tip of the iceberg" part of your problem and the easiest-to-produce answer might not be your best (production) solution.
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.