I worked on this for awhile and this was the best I could come up with...

-- SAMPLE DATA

IF OBJECT_ID('tempdb..#Weekday') IS NOT NULL DROP TABLE #Weekday; CREATE TABLE #Weekday(Weekday_id int identity primary key, [day] nvarchar(50));

IF OBJECT_ID('tempdb..#SubjectToStudy') IS NOT NULL DROP TABLE #SubjectToStudy; CREATE TABLE #SubjectToStudy(Weekday_id int,[Subject] nvarchar(50));

IF OBJECT_ID('tempdb..#output') IS NOT NULL DROP TABLE #output; CREATE TABLE #output(Weekday_id int, [day] nvarchar(50), classes nvarchar(255));

INSERT INTO #Weekday VALUES(N'MONDAY'),(N'TUESDAY'),(N'WEDNESDAY');

INSERT INTO #SubjectToStudy VALUES(1,N'PHYSICS'),(1,N'CHEMISTRY'),(1,N'MATHEMATICS'),(2,N'COMPUTERSCIENCE'),(2,N'BIOLOGY'),(3,N'BOTANY'),(3,N'PHYSICS')

INSERT INTO #output

SELECT w.Weekday_id, [day], s.[Subject]

FROM #Weekday w

JOIN #SubjectToStudy s ON w.Weekday_id=s.Weekday_id

ORDER BY Weekday_id

--THE ROUTINE:

DECLARE @classlist nvarchar(300)='';

UPDATE #output

SET @classlist=classes=(CASE WHEN @classlist='' THEN [day]+' ' ELSE @classlist+' ' END)+classes

FROM #output

WHERE Weekday_id=1

SET @classlist='';

UPDATE #output

SET @classlist=classes=(CASE WHEN @classlist='' THEN [day]+' ' ELSE @classlist+' ' END)+classes

FROM #output

WHERE Weekday_id=2

SET @classlist='';

UPDATE #output

SET @classlist=classes=(CASE WHEN @classlist='' THEN [day]+' ' ELSE @classlist+' ' END)+classes

FROM #output

WHERE Weekday_id=3;

;WITH answer AS

(SELECT m=DENSE_RANK() OVER (PARTITION BY Weekday_id ORDER BY LEN(classes) DESC),

classes

FROM #output)

SELECT classes FROM answer

WHERE m=1;

--CLEANUP

DROP TABLE #Weekday;

DROP TABLE #SubjectToStudy;

DROP TABLE #output

GO

Nice work k125