我有一個查詢與分組和總和。我有近100萬條記錄。當我運行查詢時,它需要2.5s。如果我刪除group by子句,它將花費0.89s。有沒有什麼辦法可以使用group by和sum來優化查詢。MySQL groupby與總數
SELECT aggEI.ei_uuid AS uuid,aggEI.companydm_id AS companyId,aggEI.rating AS rating,aggEI.ei_name AS name,
compdm.company_name AS companyName,sum(aggEI.count) AS activity
FROM AGG_EXTERNALINDIVIDUAL AS aggEI
JOIN COMPANYDM AS compdm ON aggEI.companydm_id = compdm.companydm_id
WHERE aggEI.ei_uuid is not null
and aggEI.companydm_id IN (8)
and aggEI.datedm_id = 20130506
AND aggEI.topicgroupdm_id IN (1,2,3,4,5,6,7)
AND aggEI.rating >= 0
AND aggEI.rating <= 100
GROUP BY aggEI.ei_uuid,aggEI.companydm_id
LIMIT 0,200000
解釋結果如下:
1 SIMPLE compdm const PRIMARY,companydm_id_UNIQUE,comp_idx PRIMARY 8 const 1 Using temporary; Using filesort
1 SIMPLE aggEI ref PRIMARY,datedm_id_UNIQUE,agg_ei_comdm_fk_idx,agg_ei_datedm_fk_idx,agg_ei_topgrp_fk_idx,uid_comp_ei_dt_idx,uid_comp_dt_idx,comp_idx datedm_id_UNIQUE 4 const 197865 Using where
而且爲什麼首先執行compdm表我不明白。有人可以解釋嗎?
我有AGG_EXTERNALINDIVIDUAL表的索引與ei_uuid,companydm_id,datedm_id的組合。在可能的關鍵字uID_comp_dt_idx下的aggEI表中顯示了相同的結果。但是aggEI表正以過時的mid_UNIQUE作爲關鍵。我不明白這種行爲。
有人可以解釋一下嗎?
查詢優化不是我的優勢,但似乎只有(companydm_id,datedm_id,topicgroupdm_id,rating)上的複合索引纔會有幫助。 – Strawberry 2013-05-13 18:17:47