SQL subquery with average of 3 top values in Postgresql - sql

Question

I need a little help to solve a query to count patients (ID) who have the average of the 3 last diastolic tension (TAD) < 90.
I've tried several type of nested subqueries with different errors.
This is my last version I've done:
SELECT CENTRO, COUNT ( DISTINCT ID )
FROM
(
SELECT PAC.CENTRO, PAC.ID, T.TAD
FROM IDDPAC PAC,
(
SELECT AVG(TA.TAD) TAD
FROM
(
SELECT
TEXT_TO_NUMBER ( PAG.TEXTO ) TAD
FROM IDDPAG PAG, DATE D
WHERE TRIM ( PAG.DGP )='AH'
AND PAG.ID=T.ID
AND PAG.FECHA=D.OMI
AND D.TIME_DATE::DATE BETWEEN DATE '2012-01-01'
AND DATE '2012-12-31'
ORDER BY PAG.FECHA DESC LIMIT 3
) TA
) T
WHERE PAC.CENTRO='10040110' AND T.ID = PAC.ID
GROUP BY PAC.CENTRO , PAC.ID
)
A
WHERE T.TAD < 90
GROUP BY CENTRO
And I get the following error:
ERROR: falta una entrada para la tabla «t» en la cláusula FROM
LINE 31: AND PAG.ID=T.ID
^
********** Error **********
Translation:
ERROR: missing an entry for the table «t» in the clause FROM
LINE 31: AND PAG.ID=T.ID
^
********** Error **********

Answer 1

To get the average of the last three values, use row_number() to enumerate the values. Then choose the last three and take the average. This gives you the patient level information:
SELECT PAC.CENTRO, PAG.ID, AVG(TA.TAD) AS TAD
FROM (SELECT PAG.ID, TEXT_TO_NUMBER ( PAG.TEXTO ) as TAD,
ROW_NUMBER() OVER (PARTITION BY PAG.ID ORDER BY D.TIME_DATE DESC) as seqnum
FROM IDDPAG PAG JOIN
DATE D
ON PAG.FECHA = D.OMI JOIN
IDDPAC PAC
ON PAC.ID = PAG.ID
WHERE TRIM ( PAG.DGP )='AH' AND
D.TIME_DATE::DATE BETWEEN DATE '2012-01-01' AND DATE '2012-12-31'
) TA
WHERE SEQNUM <= 3
GROUP BY PAC.CENTRO, PAD.ID
HAVING AVG(TA.TAD) < 90;
The count by centro would just be:
SELECT CENTRO, COUNT(*)
FROM (SELECT PAC.CENTRO, PAG.ID, AVG(TA.TAD) AS TAD
FROM (SELECT PAG.ID, TEXT_TO_NUMBER ( PAG.TEXTO ) as TAD,
ROW_NUMBER() OVER (PARTITION BY PAG.ID ORDER BY D.TIME_DATE DESC) as seqnum
FROM IDDPAG PAG JOIN
DATE D
ON PAG.FECHA = D.OMI JOIN
IDDPAC PAC
ON PAC.ID = PAG.ID
WHERE TRIM ( PAG.DGP )='AH' AND
D.TIME_DATE::DATE BETWEEN DATE '2012-01-01' AND DATE '2012-12-31'
) TA
WHERE SEQNUM <= 3
GROUP BY PAC.CENTRO, PAD.ID
HAVING AVG(TA.TAD) < 90
) TA
GROUP BY CENTRO;

Answer 2

The problem is, exactly as the error indicates, that 'T' is not defined in the place it is requested. Your error is in the innermost subquery:
SELECT
TEXT_TO_NUMBER ( PAG.TEXTO ) TAD
FROM IDDPAG PAG, DATE D
WHERE TRIM ( PAG.DGP )='AH'
AND PAG.ID=T.ID
AND PAG.FECHA=D.OMI
AND D.TIME_DATE::DATE BETWEEN DATE '2012-01-01'
AND DATE '2012-12-31'
ORDER BY PAG.FECHA DESC LIMIT 3
But there is no T defined here to be used in the PAG.ID=T.ID portion of your WHERE clause. Did you mean to join on a table called T? Or did you mean to use D.ID instead?