我有一个报告查询，其中包含2个长子查询
SELECT r1.code_centre, r1.libelle_centre, r1.id_equipe, r1.equipe, r1.id_file_attente,
r1.libelle_file_attente,r1.id_date, r1.tranche, r1.id_granularite_de_periode,r1.granularite,
r1.ContactsTraites, r1.ContactsenParcage, r1.ContactsenComm, r1.DureeTraitementContacts,
r1.DureeComm, r1.DureeParcage, r2.AgentsConnectes, r2.DureeConnexion, r2.DureeTraitementAgents,
r2.DureePostTraitement
FROM
( SELECT cc.id_centre_contact, cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe,
a.id_file_attente, f.libelle_file_attente, a.id_date, g.tranche, g.id_granularite_de_periode,
g.granularite, sum(Nb_Contacts_Traites) as ContactsTraites,
sum(Nb_Contacts_en_Parcage) as ContactsenParcage,
sum(Nb_Contacts_en_Communication) as ContactsenComm,
sum(Duree_Traitement/1000) as DureeTraitementContacts,
sum(Duree_Communication / 1000 + Duree_Conference / 1000 + Duree_Com_Interagent / 1000) as DureeComm,
sum(Duree_Parcage/1000) as DureeParcage
FROM agr_synthese_activite_media_fa_agent a, centre_contact cc,
direction_contact dc, granularite_de_periode g, media m, file_attente f
WHERE m.id_media = a.id_media
AND cc.id_centre_contact = a.id_centre_contact
AND a.id_direction_contact = dc.id_direction_contact
AND dc.direction_contact ='INCOMING'
AND a.id_file_attente = f.id_file_attente
AND m.media = 'PHONE'
AND ( ( g.valeur_min = date_format(a.id_date,'%d/%m') and g.granularite = 'Jour')
or ( g.granularite = 'Heure' and a.id_th_heure = g.id_granularite_de_periode) )
GROUP by cc.id_centre_contact, a.id_equipe, a.id_file_attente, a.id_date, g.tranche,
g.id_granularite_de_periode) r1,
(
(SELECT cc.id_centre_contact,cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe,
a.id_date, g.tranche, g.id_granularite_de_periode,g.granularite,
count(distinct a.id_agent) as AgentsConnectes,
sum(Duree_Connexion / 1000) as DureeConnexion,
sum(Duree_en_Traitement / 1000) as DureeTraitementAgents,
sum(Duree_en_PostTraitement / 1000) as DureePostTraitement
FROM activite_agent a, centre_contact cc, granularite_de_periode g
WHERE ( g.valeur_min = date_format(a.id_date,'%d/%m') and g.granularite = 'Jour')
AND cc.id_centre_contact = a.id_centre_contact
GROUP BY cc.id_centre_contact, a.id_equipe, a.id_date, g.tranche, g.id_granularite_de_periode )
UNION
(SELECT cc.id_centre_contact,cc.code_centre, cc.libelle_centre, a.id_equipe, a.equipe,
a.id_date, g.tranche, g.id_granularite_de_periode,g.granularite,
count(distinct a.id_agent) as AgentsConnectes,
sum(Duree_Connexion / 1000) as DureeConnexion,
sum(Duree_en_Traitement / 1000) as DureeTraitementAgents,
sum(Duree_en_PostTraitement / 1000) as DureePostTraitement
FROM activite_agent a, centre_contact cc, granularite_de_periode g
WHERE ( g.granularite = 'Heure'
AND a.id_th_heure = g.id_granularite_de_periode)
AND cc.id_centre_contact = a.id_centre_contact
GROUP BY cc.id_centre_contact,a.id_equipe, a.id_date, g.tranche, g.id_granularite_de_periode)
) r2
WHERE r1.id_centre_contact = r2.id_centre_contact
AND r1.id_equipe = r2.id_equipe AND r1.id_date = r2.id_date
AND r1.tranche = r2.tranche AND r1.id_granularite_de_periode = r2.id_granularite_de_periode
GROUP BY r1.id_centre_contact , r1.id_equipe, r1.id_file_attente,
r1.id_date, r1.tranche, r1.id_granularite_de_periode
ORDER BY r1.code_centre, r1.libelle_centre, r1.equipe,
r1.libelle_file_attente, r1.id_date, r1.id_granularite_de_periode,r1.tranche
EXPLAIN显示
| id | select_type | table | type| possible_keys | key | key_len | ref| rows | Extra |
'1', 'PRIMARY', '<derived3>', 'ALL', NULL, NULL, NULL, NULL, '2520', 'Using temporary; Using filesort'
'1', 'PRIMARY', '<derived2>', 'ALL', NULL, NULL, NULL, NULL, '4378', 'Using where; Using join buffer'
'3', 'DERIVED', 'a', 'ALL', 'fk_Activite_Agent_centre_contact', NULL, NULL, NULL, '83433', 'Using temporary; Using filesort'
'3', 'DERIVED', 'g', 'ref', 'Index_granularite,Index_Valeur_min', 'Index_Valeur_min', '23', 'func', '1', 'Using where'
'3', 'DERIVED', 'cc', 'ALL', 'PRIMARY', NULL, NULL, NULL, '6', 'Using where; Using join buffer'
'4', 'UNION', 'g', 'ref', 'PRIMARY,Index_granularite', 'Index_granularite', '23', '', '24', 'Using where; Using temporary; Using filesort'
'4', 'UNION', 'a', 'ref', 'fk_Activite_Agent_centre_contact,fk_activite_agent_TH_heure', 'fk_activite_agent_TH_heure', '5', 'reporting_acd.g.Id_Granularite_de_periode', '2979', 'Using where'
'4', 'UNION', 'cc', 'ALL', 'PRIMARY', NULL, NULL, NULL, '6', 'Using where; Using join buffer'
NULL, 'UNION RESULT', '<union3,4>', 'ALL', NULL, NULL, NULL, NULL, NULL, ''
'2', 'DERIVED', 'g', 'range', 'PRIMARY,Index_granularite,Index_Valeur_min', 'Index_granularite', '23', NULL, '389', 'Using where; Using temporary; Using filesort'
'2', 'DERIVED', 'a', 'ALL', 'fk_agr_synthese_activite_media_fa_agent_centre_contact,fk_agr_synthese_activite_media_fa_agent_direction_contact,fk_agr_synthese_activite_media_fa_agent_file_attente,fk_agr_synthese_activite_media_fa_agent_media,fk_agr_synthese_activite_media_fa_agent_th_heure', NULL, NULL, NULL, '20903', 'Using where; Using join buffer'
'2', 'DERIVED', 'cc', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Centre_Contact', '1', ''
'2', 'DERIVED', 'f', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_File_Attente', '1', ''
'2', 'DERIVED', 'dc', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Direction_Contact', '1', 'Using where'
'2', 'DERIVED', 'm', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'reporting_acd.a.Id_Media', '1', 'Using where'
不清楚，但我觉得这个问题似乎需要全面扫描
比我将所有子查询更改为视图（创建视图作为选择子查询），结果是相同的
感谢任何建议
答案 0 :(得分：1)
子查询和视图在大多数情况下会以相同的速度提供相同的结果。
如果您的子查询不是变量，请考虑创建与您的视图具有相同结构的表，并偶尔执行：
truncate table my_table;
insert into my_table select * from my_view;
...缓存子查询数据。如果正确编制索引，它将使在子表中存储子查询结果时丢失的时间，如果数据不经常更改，或者至少如果您不需要二至秒的最新信息，则会边缘化。