问sql优化？

如何提高一下查询语句查询速度：

SELECT ss.`NAME` xm, sc.name xy,

SUM(CASE WHEN hp.STUDENT_ID = cj.id THEN cj.fs else 0 END) zf

FROM (SELECT hs.ID id,hs.SCORE*hi.WEIGHT/100 fs,hi.`NAME` item

FROM health_item hi,health_score hs

where hs.IS_DELETED = 0

AND hi.IS_SURVEY = 1

AND hs.ITEM_ID = hi.ID

)cj,health_person hp

LEFT JOIN school_student ss ON hp.STUDENT_ID = ss.ID

LEFT JOIN school_college sc ON ss.SCHOOL_COLLEGE_ID = sc.ID

WHERE hp.IS_DELETED = 0

GROUP BY hp.STUDENT_ID