使用ORDER BY时查询速度慢

也许这会有所帮助：

SELECt * FROM (         SELECt      Course.CourseID,      Course.Description,      UserCourse.UserID,      UserCourse.TimeAllowed,      UserCourse.CreatedOn,      UserCourse.PassedOn,      UserCourse.IssuedOn,      C.LessonCnt    FROM      UserCourse    INNER JOIN      Course    USING(CourseID)    INNER JOIN    (      SELECt CourseID, COUNT(*) AS LessonCnt FROM CourseSection GROUP BY CourseID    ) C    USING(CourseID)    WHERe       UserCourse.UserID = 8810) ORDER BY CourseID