calculating values to be used later in Oracle SQL
- From: William Threlfall <William.Threlfall@xxxxxxxxxxxxxxxxxxxxxxxx>
- To: "Oracle-L@xxxxxxxxxxxxx" <Oracle-L@xxxxxxxxxxxxx>
- Date: Fri, 21 Feb 2014 10:10:11 -0700
Question for the SQL experts ...
I need to calculate a value and then use it many times as a criterion for 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 subquery gives me the date of last transplant:
(TO_DATE((MAX(PT.DATE_OF_TRANS) OVER (PARTITION BY PT.PAT_ID ORDER 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 nuisance way 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 think there ought to be 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
________________________________
This message and any attached documents are only for the use of the intended
recipient(s), are confidential and may contain privileged information. Any
unauthorized review, use, retransmission, or other disclosure is strictly
prohibited. If you have received this message in error, please notify the
sender immediately, and then delete the original message. Thank you.
Other related posts:
