Вычисление медианы в SQL Server 2008 R2

Question

Мне нужно вычислить медианную для нескольких полей в запросе и сгруппировать ее одним из столбцов. Есть ли способ легко вычислить Median в SQL Server 2008 R2? У меня возникают проблемы с его вычислением в 2008 R2.

Table structure: 
PatientName (need to calculate count group by PatientType) 
PatientType (should be used to group the query by), 
minutes1, 
minutes2, 
minutes3, 
minutes4, 
minutes5 

End Result: 
PatientCount (Group by PatientType), 
Median For minutes1 (Group by PatientType), 
Median For minutes2 (Group by PatientType), 
Median For minutes3 (Group by PatientType), 
Median For minutes4 (Group by PatientType), 
Median For minutes5 (Group by PatientType) 

Answer 1

Вы можете попробовать это:

SELECT PatientType, minutes1=(
    SELECT AVG(1.0 * minutes1) 
    FROM 
    (
    SELECT t3.minutes1, rn = ROW_NUMBER() OVER (ORDER BY t3.minutes1), c.c 
    FROM (SELECT minutes1 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t3 
    CROSS JOIN (SELECT c = COUNT(*) FROM (SELECT minutes1 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t4) AS c 
) AS x 
    WHERE rn IN ((c + 1)/2, (c + 2)/2) 
), minutes2=(
    SELECT AVG(1.0 * minutes2) 
    FROM 
    (
    SELECT t3.minutes2, rn = ROW_NUMBER() OVER (ORDER BY t3.minutes1), c.c 
    FROM (SELECT minutes2 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t3 
    CROSS JOIN (SELECT c = COUNT(*) FROM (SELECT minutes2 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t4) AS c 
) AS x 
    WHERE rn IN ((c + 1)/2, (c + 2)/2) 
), minutes3=(
    SELECT AVG(1.0 * minutes1) 
    FROM 
    (
    SELECT t3.minutes3, rn = ROW_NUMBER() OVER (ORDER BY t3.minutes1), c.c 
    FROM (SELECT minutes3 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t3 
    CROSS JOIN (SELECT c = COUNT(*) FROM (SELECT minutes3 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t4) AS c 
) AS x 
    WHERE rn IN ((c + 1)/2, (c + 2)/2) 
), minutes4=(
    SELECT AVG(1.0 * minutes4) 
    FROM 
    (
    SELECT t3.minutes1, rn = ROW_NUMBER() OVER (ORDER BY t3.minutes1), c.c 
    FROM (SELECT minutes4 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t3 
    CROSS JOIN (SELECT c = COUNT(*) FROM (SELECT minutes4 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t4) AS c 
) AS x 
    WHERE rn IN ((c + 1)/2, (c + 2)/2) 
), minutes5=(
    SELECT AVG(1.0 * minutes5) 
    FROM 
    (
    SELECT t3.minutes1, rn = ROW_NUMBER() OVER (ORDER BY t3.minutes1), c.c 
    FROM (SELECT minutes5 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t3 
    CROSS JOIN (SELECT c = COUNT(*) FROM (SELECT minutes5 FROM Table t2 WHERE t1.PatientType=t2.PatientType) t4) AS c 
) AS x 
    WHERE rn IN ((c + 1)/2, (c + 2)/2) 
) 
FROM Table t1 
GROUP BY PatientType 

и есть, вероятно, гораздо лучше, и это, вероятно, может быть оптимизирован совсем немного.