mysql - Merge two similar aggregate functions in select statement -

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here's sql statement:

select distinct  `class`, `student_id` , `student_name`, (      select sum(  `credits` )       `stumgr_scores` b     join  `stumgr_courses` using (  `course_id` )       `year` =2012 , a.`student_id` = b.`student_id` )  `total_credits`, (      select sum( `credits` *  `final_score` )      `stumgr_scores` c     join  `stumgr_courses` using (  `course_id` )       `year` =2012 , a.`student_id` = c.`student_id` ) `total_scores`  `stumgr_scores` natural join  `stumgr_students`   `year` =2012 ,  `grade` =2011

you may discover these 2 select statement use aggregate functions similar. so, want merge them 1 following:

select distinct  `class`, `student_id` , `student_name`, (      select          sum(  `credits` )  `total_credits`,          sum( `credits` *  `final_score` )  `total_scores`      `stumgr_scores` b     join  `stumgr_courses` using (  `course_id` )       `year` =2012 , a.`student_id` = b.`student_id` ) `something`  `stumgr_scores` natural join  `stumgr_students`   `year` =2012 ,  `grade` =2011

of course, sql statement above doesn't work , don't know do. besides, query slow because of large data, have suggestions? lot.

i have had guess @ table structure slightly, should able simplify query massively using joins rather correlated subqueries:

select  st.student_id,         st.student_name,         c.class,         sum(sc.credits) total_credits,         sum(sc.credits * sc.final_score) total_scores    stumgr_students st         inner join stumgr_scores sc             on sc.student_id = st.student_id         inner join stumgr_courses c             on c.course_id = st.course_id group st.student_id, st.student_name, c.class;

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