SQL - Ik moet een totale waarde verdelen over meerdere rijen in een andere tabel

U kunt het als volgt doen, deze zoekopdracht vult eerst de klaslokalen met de grootste capaciteit:

DECLARE @School TABLE (School_Id INT,Course_Id 
    VARCHAR(50), Total_Students INT)
DECLARE @Class TABLE (School_Id INT,Course_Id 
    VARCHAR(50), Class_ID VARCHAR(50), Capacity INT)
INSERT @School VALUES 
   (1,         'Acct101'        ,150),
   (1,         'Acct102'        ,100),
   (2,         'Acct101'        ,110),
   (2,         'Acct102'        ,130)
INSERT @Class VALUES 
   (1,         'Acct101'     ,'A1'       ,65),
   (1,         'Acct101'     ,'A2'       ,50),
   (1,         'Acct101'     ,'A3'       ,70),
   (1,         'Acct102'     ,'Ab1'      ,100),
   (1,         'Acct102'     ,'Ab2'      ,100),
   (2,         'Acct101'     ,'B1'       ,80),
   (2,         'Acct101'     ,'B2'       ,90)

;WITH y AS (
SELECT  a.*,
        ROW_NUMBER() OVER 
            (PARTITION BY a.School_ID, a.Course_ID ORDER BY a.Capacity DESC) 
            CapacitiyOrderPerSchoolAndCourse,
        SUM(a.Capacity) OVER 
            (PARTITION BY a.School_ID, a.Course_ID) 
            TotalCapacityForSchoolAndCourse,
        b.Total_Students TotalParticipants
FROM    @Class a
JOIN    @School b ON 
        b.School_Id = a.School_Id
        AND b.Course_Id = a.Course_Id
), z AS(
SELECT  x.School_Id, 
        x.Course_Id, 
        y.TotalCapacityForSchoolAndCourse, 
        y.TotalParticipants,
        CASE WHEN y.TotalParticipants < SUM(x.Capacity) THEN 
                y.TotalParticipants
            ELSE 
                SUM(x.Capacity) 
            END NumberOfStudentsInClasses,
        MIN(y.Capacity) ClassCapacity,
        y.Class_ID ClassName,
        MIN(y.Capacity) - 
        CASE WHEN y.TotalParticipants - SUM(x.Capacity) < 0 THEN 
               ABS(y.TotalParticipants - SUM(x.Capacity))
            ELSE
               0
            END StudentsInClass
FROM    y
JOIN    y x ON x.School_Id = y.School_Id 
        AND x.Course_Id = y.Course_Id 
        AND x.CapacitiyOrderPerSchoolAndCourse 
                <= y.CapacitiyOrderPerSchoolAndCourse
GROUP   BY x.School_Id, 
        x.Course_Id, 
        y.CapacitiyOrderPerSchoolAndCourse, 
        y.Class_ID, 
        y.TotalCapacityForSchoolAndCourse, 
        y.TotalParticipants
)

SELECT  
        z.School_Id, 
        z.Course_Id, 
        z.TotalCapacityForSchoolAndCourse, 
        z.TotalParticipants,
        z.ClassName,
        z.ClassCapacity,
        CASE WHEN StudentsInClass < 0 THEN 
                0 
            ELSE 
                StudentsInClass 
            END StudentsInClass
FROM    z

Als je wilt dat elk klaslokaal een bepaald aantal studenten heeft, kun je het als volgt doen (het wijst een aantal studenten toe aan elk klaslokaal op basis van zijn capaciteit):

;WITH y AS (
SELECT  a.*,
        SUM(a.Capacity) OVER 
            (PARTITION BY a.School_ID, a.Course_ID) 
            AS TotalCapacityForSchoolAndCourse,
        b.Total_Students TotalParticipants
FROM    @Class a
JOIN    @School b ON 
        b.School_Id = a.School_Id
        AND b.Course_Id = a.Course_Id
), z AS(
SELECT  y.School_Id, 
        y.Course_Id, 
        y.TotalCapacityForSchoolAndCourse, 
        y.TotalParticipants,
        MIN(y.Capacity) ClassCapacity,
        y.Class_ID,
        MIN(y.Capacity) * 1.0 / y.TotalCapacityForSchoolAndCourse 
            AS PercentOfCapacity,
        ROUND(
            MIN(y.Capacity) * 1.0 / y.TotalCapacityForSchoolAndCourse 
                * TotalParticipants
            , 0, 0) 
            AS NumberOfStudents
FROM    y
GROUP   BY y.School_Id, 
        y.Course_Id, 
        y.Class_ID, 
        y.TotalCapacityForSchoolAndCourse, 
        y.TotalParticipants
)
, i AS(
SELECT  
        z.School_Id, 
        z.Course_Id, 
        z.TotalCapacityForSchoolAndCourse, 
        z.TotalParticipants,
        z.Class_ID,
        z.ClassCapacity,
        PercentOfCapacity,
        NumberOfStudents,
        SUM(NumberOfStudents) OVER 
            (PARTITION BY z.School_Id, z.Course_Id) 
            AS SumNumberOfStudents,
        ROW_NUMBER() OVER 
            (PARTITION BY z.School_Id, z.Course_Id 
                ORDER BY NumberOfStudents) 
            AS ClassWithSmallestCapacity
FROM    z
), j AS(
SELECT  i.School_Id, 
        i.Course_Id, 
        i.TotalCapacityForSchoolAndCourse, 
        i.TotalParticipants,
        i.Class_ID,
        i.ClassCapacity,
        i.PercentOfCapacity,
        i.NumberOfStudents,
        i.NumberOfStudents +
        CASE WHEN ClassWithSmallestCapacity = 1 THEN 
                TotalParticipants - SumNumberOfStudents 
            ELSE 0 
            END AS NumberOfStudents2
FROM    i
)

SELECT  *
FROM    j