Re: calculating values to be used later in Oracle SQL

The new_value parameter to the column directive should help you:

column lasttx new_value last_tx

Now you can use &last_tx throughout the transaction or script:

...
where x.date_of_lab > &last_tx
...





 
David Fitzjarrell
Primary author, "Oracle Exadata Survival Guide"




On Friday, February 21, 2014 10:11 AM, William Threlfall <William.Threlfall_at_albertahealthservices.ca> wrote:
 
 
Question for the SQL experts …
I need to calculate a value and then use it many times as a criterionfor other selections.  What is the best way to do that in Oracle SQL?
For example, I need to calculate, for each patient, the date of last transplant (call it LASTTX) and then select a bunch of lab results where one of the criteria in the WHERE clause would be DATE_OF_LAB
> LASTTX.  
 
In the following example I want to select the greatest non-NULL CREAT lab result from the most recent DATE_OF_LAB where the DATE_OF_LAB is greater than the date of last transplant.
 
This subquerygives me the date of last transplant:
 
  (TO_DATE((MAX(PT.DATE_OF_TRANS) OVER (PARTITION BY PT.PAT_IDORDER BY PT.PAT_ID
    ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)), 'yyyy.mm.dd')) AS LASTTX,       
 
However, if I try to use LASTTX in subsequent SELECT subquery statements, I get an error that it is an invalid identifier.
 
Is there a way to do what I want without having to use that code snippet dozens of times, as in:
 
  (SELECT MAX(CREAT) KEEP (DENSE_RANK FIRST ORDER BY X.DATE_OF_LAB DESC, X.CREAT DESC)
    FROM PATIENT_LABS X
    WHERE X.CREAT IS NOT NULL 
    AND X.PAT_ID = PD.PAT_ID    
    AND X.DATE_OF_LAB > LASTTX) AS MRCREAT
 
The nuisanceway would be to re-use that code snippet over and over again, such as:
 
  (SELECT MAX(CREAT) KEEP (DENSE_RANK FIRST ORDER BY X.DATE_OF_LAB DESC, X.CREAT DESC)
    FROM PATIENT_LABS X
    WHERE X.CREAT IS NOT NULL 
    AND X.PAT_ID = PD.PAT_ID    
    AND X.DATE_OF_LAB > 
       (SELECT MAX(PT.DATE_OF_TRANS) OVER (PARTITION BY PT.PAT_ID ORDER BY PT.PAT_ID
        ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
        FROM PAT_TRANSPLANT PT)
  )AS MRCREAT
 
I thinkthere ought tobe a way to calculate variables and use them later on, but I’m just not clueing in at the moment.
 
Thanks, - Bill.
 
_______________________________________
Willliam J. (Bill) Threlfall, MSc
Clinical Informatics Coordinator - OTTR
Transplant Services, University of Alberta Hospital
Alberta Health Services
Aberhart Centre, Room 9221
8440 112 Street
Edmonton, AB T6G 2B7
 
Telephone: 780-407-6175  FAX: 780-407-8981
 
Alberta Health Services
www.albertahealhservices.ca
 
 
 
 

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