Select Latest or most recent date in SQL query - sql

Question

I am running a query in SQL on our EHR/EMR database. I am primarily looking at an assessment that is done by a nurse during each patient encounter/visit and looking to return an answer for the most recent assessment date along with some other info. I have the query created and all the data is coming over, however, it is returning all assessment dates and the answers instead of just the latest date and answer. I'll attach the full code below.
SELECT DISTINCT
MAX(PTA.ASSESSMENT_DATE) AS Max_Date,
SAQ.QUESTION_TEXT, SAA.ANSWER_TEXT, dbo.PT_BASIC.PATIENT_CODE,
dbo.PT_BASIC.NAME_FULL
FROM
dbo.PTC_ASSESSMENT_ANSWER AS PAA
INNER JOIN
dbo.PTC_ASSESSMENT AS PTA ON PTA.ASSESSMENT_ID = PAA.ASSESSMENT_ID
AND PTA.PATIENT_ID = PAA.PATIENT_ID
INNER JOIN
dbo.SYS_ASSESSMENT_POINTER AS SAP ON SAP.POINTER_ID = PAA.POINTER_ID
INNER JOIN
dbo.SYS_ASSESSMENT_QUESTION AS SAQ ON SAQ.QUESTION_ID = SAP.QUESTION_ID
INNER JOIN
dbo.SYS_ASSESSMENT_ANSWER AS SAA ON SAA.ANSWER_ID = SAP.ANSWER_ID
INNER JOIN
dbo.PT_BASIC ON PTA.PATIENT_ID = dbo.PT_BASIC.PATIENT_ID
WHERE
(PTA.ASSESSMENT_DATE BETWEEN CONVERT(DATETIME, '2017-09-05 00:00:00', 102)
AND CONVERT(DATETIME, '2017-10-12 00:00:00', 102))
GROUP BY
dbo.PT_BASIC.PATIENT_CODE, dbo.PT_BASIC.NAME_FULL, SAQ.QUESTION_TEXT,
SAA.ANSWER_TEXT
HAVING
(SAA.ANSWER_TEXT LIKE '%LEVEL % -%')
The current output would be something similar to this:
9/5/2017 PATIENT ABC Answer1
9/6/2017 PATIENT ABC Answer2
9/7/2017 PATIENT ABC Answer3
9/6/2017 PATIENT XYZ Answer4
What I am expecting is:
9/7/2017 PATIENT ABC Answer3
9/6/2017 PATIENT XYZ Answer4

Answer 1

If your version of SQL Server supports it, using ROW_NUMBER() OVER() is an efficient and simple method for arriving at "latest" (or "earliest") rows from a single table. However as we know so little about your data model it isn't easy to guess how to reduce the rows to just the "lastest answer" which probably requires a more complex subquery. However you can still use ROW_NUMBER() OVER() on that subquery. I suspect that the nature of questions and answers is that the table aliases SAP, SAQ, SAA may all need to be involved in this subquery.
Note that instead of directly joining PTA this is now a subquery and the join condition to the outer query requires that RN=1 which is the row with the "latest" date.
SELECT
MAX(PTA.ASSESSMENT_DATE) AS Max_Date
, SAQ.QUESTION_TEXT
, SAA.ANSWER_TEXT
, dbo.PT_BASIC.PATIENT_CODE
, dbo.PT_BASIC.NAME_FULL
FROM dbo.PTC_ASSESSMENT_ANSWER AS PAA
INNER JOIN (
SELECT
*
, ROW_NUMBER() OVER (PARTITION BY PATIENT_ID
ORDER BY ASSESSMENT_DATE DESC) AS RN
FROM dbo.PTC_ASSESSMENT
WHERE ASSESSMENT_DATE BETWEEN '20170905' AND '20171012'
) AS PTA ON PTA.ASSESSMENT_ID = PAA.ASSESSMENT_ID
AND PTA.PATIENT_ID = PAA.PATIENT_ID
AND PTA.RN = 1
INNER JOIN dbo.SYS_ASSESSMENT_POINTER AS SAP ON SAP.POINTER_ID = PAA.POINTER_ID
INNER JOIN dbo.SYS_ASSESSMENT_QUESTION AS SAQ ON SAQ.QUESTION_ID = SAP.QUESTION_ID
INNER JOIN dbo.SYS_ASSESSMENT_ANSWER AS SAA ON SAA.ANSWER_ID = SAP.ANSWER_ID
INNER JOIN dbo.PT_BASIC ON PTA.PATIENT_ID = dbo.PT_BASIC.PATIENT_ID
WHERE SAA.ANSWER_TEXT LIKE '%LEVEL % -%'
GROUP BY
dbo.PT_BASIC.PATIENT_CODE
, dbo.PT_BASIC.NAME_FULL
, SAQ.QUESTION_TEXT
, SAA.ANSWER_TEXT
select distinct is not required on this query (or any similar query using GROUP BY)
yyymmdd is the safest date literal in SQL Server, you don't need the converts using style 102
your having clause should be moved to a where clause as it does not evaluate any aggregated value

Answer 2

Cross apply allows you to use a correlated query and chive the top most n records ordered by date desc for each patient assessment. (after review maybe you just need patient?)
Perhaps just change:
INNER JOIN
dbo.PTC_ASSESSMENT AS PTA ON PTA.ASSESSMENT_ID = PAA.ASSESSMENT_ID
AND PTA.PATIENT_ID = PAA.PATIENT_ID
TO:
CROSS APPLY (SELECT TOP 1 *
FROM dbo.PTC_ASSESSMENT PTA2
WHERE PTA2.ASSESSMENT_ID = PAA.ASSESSMENT_ID
/*AND PTA2.PATIENT_ID = PAA.PATIENT_ID*/
ORDER BY PTA2.Assessment_date desc) PTA
GIVING YOU: (I left the /AND PTA2.PATIENT_ID = PAA.PATIENT_ID/ --I think you can omit this. I left the */ in place but it's not needed)
SELECT MAX(PTA.ASSESSMENT_DATE) AS Max_Date
, SAQ.QUESTION_TEXT
, SAA.ANSWER_TEXT
, dbo.PT_BASIC.PATIENT_CODE
, dbo.PT_BASIC.NAME_FULL
FROM dbo.PTC_ASSESSMENT_ANSWER AS PAA
CROSS APPLY (SELECT TOP 1 *
FROM dbo.PTC_ASSESSMENT PTA2
WHERE PTA2.ASSESSMENT_ID = PAA.ASSESSMENT_ID --I think you can omit this.
/*AND PTA2.PATIENT_ID = PAA.PATIENT_ID*/
ORDER BY PTA2.Assessment_date desc) PTA
INNER JOIN dbo.SYS_ASSESSMENT_POINTER AS SAP
ON SAP.POINTER_ID = PAA.POINTER_ID
INNER JOIN dbo.SYS_ASSESSMENT_QUESTION AS SAQ
ON SAQ.QUESTION_ID = SAP.QUESTION_ID
INNER JOIN dbo.SYS_ASSESSMENT_ANSWER AS SAA
ON SAA.ANSWER_ID = SAP.ANSWER_ID
INNER JOIN dbo.PT_BASIC
ON PTA.PATIENT_ID = dbo.PT_BASIC.PATIENT_ID
WHERE (PTA.ASSESSMENT_DATE BETWEEN CONVERT(DATETIME, '2017-09-05 00:00:00', 102) AND CONVERT(DATETIME, '2017-10-12 00:00:00', 102))
GROUP BY dbo.PT_BASIC.PATIENT_CODE
, dbo.PT_BASIC.NAME_FULL
, SAQ.QUESTION_TEXT
, SAA.ANSWER_TEXT
HAVING (SAA.ANSWER_TEXT LIKE '%LEVEL % -%')
It appears you're not concerned about patients w/o assessments as all your joins are inner or we could use OUTER APPPLY to be sure to keep all answers regardless if an assessment has been provided.
Alternatively you could use a row_number() logic ( Tab Alleman's link has this covered) and a cte; but if cross apply is available might as well use it here.

Answer 3

Please include order by PTA.ASSESSMENT_DATE DESC to see the latest records at the top.