Вычислить статистический режим в SQL Server 2005

Question

У меня есть эти 2 таблицы: Курс (PK CourseId, Title) и Attendee (PK AttendeeId, FK CourseId, Method).
Многие участники могут пройти курс по любому из 6 методов.

Как распечатать одну запись для каждого курса в таблице курса (CourseId, Title) со статистическим режимом метода для всех участников каждого курса?

Answer 1

ОК, от того, что я понимаю, вам нужно.

С этой Mode (statistics),

Режим не обязательно уникален, так же, максимальная частота может быть достигнута при различных значениях.

Так здесь идет

DECLARE @Course TABLE(
     CourseID INT, 
     Title VARCHAR(50) 
) 

INSERT INTO @Course (CourseID,Title) SELECT 1, 'AA' 
INSERT INTO @Course (CourseID,Title) SELECT 2, 'BB' 
INSERT INTO @Course (CourseID,Title) SELECT 3, 'CC' 

DECLARE @Attendee TABLE(
     AttendeeID INT, 
     CourseID INT, 
     Method INT 
) 

INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 1, 1, 1 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 2, 1, 1 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 3, 1, 2 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 4, 1, 1 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 5, 1, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 6, 1, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 7, 1, 4 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 8, 1, 4 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 9, 1, 5 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 10, 1, 6 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 11, 1, 6 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 12, 1, 6 

INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 13, 2, 1 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 14, 2, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 15, 2, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 16, 2, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 17, 2, 3 
INSERT INTO @Attendee (AttendeeID,CourseID,Method) SELECT 18, 2, 6 

DECLARE @Counts TABLE(
     CourseID INT, 
     Title VARCHAR(50), 
     Method INT, 
     NumberMethodPerCourse INT 
) 

INSERT INTO @Counts (CourseID,Title,Method,NumberMethodPerCourse) 
SELECT c.CourseID, 
     c.Title, 
     a.Method, 
     COUNT(a.Method) NumberMethodPerCourse 
FROM @Course c INNER JOIN 
     @Attendee a ON c.CourseID = a.CourseID 
GROUP BY c.CourseID, 
      c.Title, 
      a.Method 

SELECT CourseMax.CourseID, 
     CourseMax.Title, 
     CourseMax.MaxNumber, 
     Counts.Method 
FROM (
      SELECT Counts.CourseID, 
        Counts.Title, 
        MAX(NumberMethodPerCourse) MaxNumber 
      FROM @Counts Counts 
      GROUP BY Counts.CourseID, 
         Counts.Title 
     ) CourseMax INNER JOIN 
     @Counts Counts ON CourseMax.CourseID = Counts.CourseID 
         AND CourseMax.MaxNumber = Counts.NumberMethodPerCourse