Query Builder - Unique Records

[#1]

Hello ,

After quite a bit of personal struggle to solve my problem, I've decided to post it as a question to user and JMP community.

Have a database from which p1, p2, asset and time are pulled from. Database is an accumulating database which means parameters p1, and p2 are loaded as representing the last state for each asset at a specific time. In other words, prior older instances of p1 and p2 are invalid, and the most recent versions of p1 and p2 are needed for a given asset at the latest reported time.

Hence, what  I need is an descending order via time and then force the outcome to be unique at asset level.

Any ideas of how I need to direct this in query builder ?

I rather prefer to have a solution by not using a custom SQL.... I actually have a solution at Custom SQL but I like to learn how to do this within query builder as I will be adding a few more pieces which be hard to do in the Custom SQL

Appreciate the help.

Altug Bayram

[#2]

If it's a duplicate entry perhaps using the DISTINCT keyword will help.

[#3 · Accepted solution]

DISTINCT won't help the OP, because there really aren't any distinct rows here.

I found a query that would solve the second case.  I added 6 rows at the bottom that duplicate the max times for each asset, plus added an X variable.  Here is the table:

And here is the query that works (it requires one subquery and one subquery within a subquery)):

The custom expression is:

t1.Time = (SELECT MAX(tInner.Time) FROM parts tInner WHERE t1.Asset = tInner.Asset)

AND

t1.X = (SELECT MAX(tInner.X) FROM parts tInner WHERE t1.Asset = tInner.Asset AND

   tInner.Time = (SELECT MAX(tInner2.Time) FROM parts tInner2 WHERE tInner.Asset = tInner2.Asset))

I capitalized all the SQL keywords to make it easier to read.  I tried some simpler queries, but they did not work.

HTH,

Eric

[#4]

Eric,

It worked like a charm ...

I am wondering though ... would it have also worked by running the first original version of custom epxression (with only Time) AND while choosing X aggregation as "Maximum" inside "Included Columns" field ... ?

thanks so much ....

[#5]

Running the original version with only Time and using the MAX aggregation on X can be made to return the correct rows, but you will not be able to find out the values of p1 and p2 for those rows.  If I do what you said leaving p1 and p2 in the query I get all the rows with the duplicate max times, because p1 and p2 become GROUP BY's for the query:

Now, if I take p1 and p2 out of the query, the query returns the correct rows:

but the whole point was to find the values of p1 and p2 for those rows, and they are gone.  So I think the double subquery approach is the only approach that answers the question you asked.

Eric

[#6]

Eric,

I understand better now and agree w/ you . Again , thanks for the effort you provided to this issue.

Your help has been very valuable.

[#7]

My pleasure.  This thread really pushed my understanding of subqueries.  I learned a lot.

Take care,

Eric