I wish I could correlate an "inline view"...

Question

I have a Patient table:

PatientId   Admitted
---------   ---------------
1    d/m/yy hh:mm:ss
2    d/m/yy hh:mm:ss
3    d/m/yy hh:mm:ss

I have a PatientMeasurement table (0 to many):

PatientId   MeasurementId Recorded  Value
---------   ------------- ---------------  -----
1    A  d/h/yy hh:mm:ss  100
1    A  d/h/yy hh:mm:ss  200
1    A  d/h/yy hh:mm:ss  300
2    A  d/h/yy hh:mm:ss  10
2    A  d/h/yy hh:mm:ss  20
1    B  d/h/yy hh:mm:ss  1
1    B  d/h/yy hh:mm:ss  2

I am trying to create a result set that resembles:

PatientId   Numerator Denominator
---------   -------- -----------
1    1  1
2    1  1
3    0  1

Essentially, a patient will have a 1 in the numerator if the have at least one value for measurement A and one value for measurement B. In this example, patient 1 has 3 A measurements and 2 B measures, so the numerator is 1. Patient 2 has 2 A measurements, but no B measurements, so the numerator is 0. Patient has neither an A measurement nor a B measurement, so the numerator is 0.

My query thus far is:

SELECT  PatientId, CASE WHEN a.cnt+b.cnt>2 THEN 1 ELSE 0 END Numerator, 1 Denominator
FROM    patient p

LEFT OUTER JOIN (
    SELECT PatientId, count(*) cnt
    FROM PatientMeasurement pm
    WHERE MeasurementId='A'
    --AND Recorded <= dateadd(hh, 12, Admitted)
    GROUP BY PatientId
) a ON p.PatientId=a.PatientId

LEFT OUTER JOIN (
    SELECT PatientId, count(*) cnt
    FROM PatientMeasurement pm
    WHERE MeasurementId='B'
    --AND Recorded <= dateadd(hh, 12, Admitted)
    GROUP BY PatientId
) b ON p.PatientId=b.PatientId

This works as expected as long as I don't include the correlated, date restriction (Recorded < dateadd(hh, 12, Admitted). Unfortunately, correlating an 'inline view' in this manner is not syntactically valid.

This has forced me to re-write the SQL to:

SELECT  PatientId, CASE WHEN v.a+v.b>2 THEN 1 ELSE 0 END Numerator, 1 Denominator
FROM    (

    SELECT PatientId,
    (
     SELECT PatientId, count(*) cnt
     FROM PatientMeasurement pm
     WHERE PatientId=p.PatientId
     AND MeasurementId='A'
     AND Recorded <= dateadd(hh, 12, Admitted)
     GROUP BY PatientId
    ) a,
    (
     SELECT PatientId, count(*) cnt
     FROM PatientMeasurement pm
     WHERE PatientId=p.PatientId
     AND MeasurementId='B'
     AND Recorded <= dateadd(hh, 12, Admitted)
     GROUP BY PatientId
    ) b
    FROM Patient p
) v

My question: Is there a better, more-efficient way to do this?

Thanks for your time.

Answer 1

Try this :

WITH GroupPatients AS 
    (SELECT MeasurementID, PatientId, Count(*) AS cnt
    FROM PatientMeasurement AS pm
    INNER JOIN Patient p ON pm.PatientID = p.PatientID
    WHERE
     MeasurementId IN ('A', 'B')
    AND
     Recorded <= dateadd(hh, 12, Admitted)
    GROUP BY MeasureMentID, PatientId)

SELECT p.PatientID, Case
    When IsNull(GPA.cnt, 0) > 0 AND IsNull(GPB.cnt, 0) > 0 Then 1
    Else 0
End AS Numerator, 1 AS Denominator
FROM Patient p
LEFT JOIN GroupPatientsA AS GPA ON p.PatientID = GPA.PatientID AND GPA.MeasurementID = 'A'
LEFT JOIN GroupPatientsB AS GPB ON p.PatientID = GPB.PatientID AND GPB.MeasurementID = 'B'

I've made one tweak to the business logic too - your spec says Numerator should be one if a patient has both A and B measurements - however, your clause of a.cnt+b.cnt>2 will erroneously return one if either a.cnt or b.cnt are 3 or more and the other is zero.

Answer 2

SELECT  p.*, 
        CASE WHEN
        EXISTS
        (
        SELECT  NULL
        FROM    PatientMeasurement pm
        WHERE   pm.PatientID = p.ID
                AND pm.Type = 'A'
                AND pm.Recorded <= DATEADD(hh, 12, p.Admitted)
        ) AND EXISTS (
        SELECT  NULL
        FROM    PatientMeasurement pm
        WHERE   pm.PatientID = p.ID
                AND pm.Type = 'B'
                AND pm.Recorded <= DATEADD(hh, 12, p.Admitted)
        ) THEN 1 ELSE 0 END
FROM    Patient p

Answer 3

Another solution can be close to your original attempt using OUTER APPLY:

SELECT  PatientId, CASE WHEN a.cnt+b.cnt>2 THEN 1 ELSE 0 END Numerator, 1 Denominator 
FROM    patient p 
OUTER APPLY ( 
    SELECT      count(*) cnt 
    FROM        PatientMeasurement pm 
    WHERE       MeasurementId='A' 
    AND       Recorded <= dateadd(hh, 12, p.Admitted) 
    AND pm.PatientId = p.PatientId
) AS a(cnt)     
OUTER APPLY ( 
    SELECT      count(*) cnt 
    FROM        PatientMeasurement pm 
    WHERE       MeasurementId='B' 
    AND       Recorded <= dateadd(hh, 12, p.Admitted) 
    AND pm.PatientId = p.PatientId
) AS b(cnt)

Answer 4

Assuming you are using Sql 2005 or 2008, the entire query can be simplified using some window functions and a pivot:

with pData as
(
 select count(*) over(partition by PatientId, MeasurementId) as cnt,
   PatientId, MeasurementId
 from PatientMeasurement pm
 where MeasurementId in('A','B')
 and  Recorded <= dateadd(hh, 12, Admitted)
)
select PatientId, coalesce([A],0) as cntA, coalesce([B],0) as cntB,
  case when coalesce([A],0) + coalesce([B],0) > 2 then 1 else 0 end as Numerator,
  1 as Denominator
from pData
pivot (max(cnt) for MeasurementId in([A],[B])) pvt

Answer 5

DECLARE @TimeSlot int;
SET @TimeSlot = 12;

WITH 
pt AS (
    SELECT p.PatientID, p.Admitted, m.MeasurementID, m.Recorded,
     CASE 
       WHEN m.Recorded <= dateadd(hh, @TimeSlot, p.Admitted) THEN 1 
       ELSE 0 
     END AS "InTimeSlot"
    FROM Patient AS p
    LEFT JOIN PatientMeasurement AS m ON p.PatientID = m.PatientID
),
cntA AS (
    SELECT PatientID, count(*) AS "A_count"
    FROM pt WHERE MeasurementID='A' AND InTimeSlot = 1
    GROUP BY PatientID
),
cntB AS (
    SELECT PatientID, count(*) AS "B_count"
    FROM pt WHERE MeasurementID='B' AND InTimeSlot = 1
    GROUP BY PatientID
),
cntAB AS (
    SELECT p.PatientID
       ,coalesce(a.A_count, 0) AS "A_cnt"
       ,coalesce(b.B_count, 0) AS "B_cnt"
    FROM Patient as p
    LEFT JOIN  cntA  AS a ON p.PatientID = a.PatientID
    LEFT JOIN  cntB  AS b ON p.PatientID = b.PatientID
),
cntN AS (
    SELECT PatientID,
     CASE WHEN A_cnt > 0 AND B_cnt > 0 THEN 1 ELSE 0 END AS Numerator
    FROM cntAB 
)
SELECT PatientID, Numerator, 1 AS Denominator FROM cntN