我正在尝试执行计数以获取分页中的结果总数，但查询速度太慢 2.12s
+-------+
| size |
+-------+
| 50000 |
+-------+
1 row in set (2.12 sec)
我的计数查询
select count(appeloffre0_.ID_APPEL_OFFRE) as size
from ao.appel_offre appeloffre0_
inner join ao.acheteur acheteur1_
on appeloffre0_.ID_ACHETEUR=acheteur1_.ID_ACHETEUR
where
(exists (select 1 from ao.lot lot2_ where lot2_.ID_APPEL_OFFRE=appeloffre0_.ID_APPEL_OFFRE and lot2_.ESTIMATION_COUT>=1))
and (exists (select 1 from ao.lieu_execution lieuexecut3_ where lieuexecut3_.appel_offre=appeloffre0_.ID_APPEL_OFFRE and lieuexecut3_.region=1))
and (exists (select 1 from ao.ao_activite aoactivite4_ where aoactivite4_.ID_APPEL_OFFRE=appeloffre0_.ID_APPEL_OFFRE and (aoactivite4_.ID_ACTIVITE=1)))
and appeloffre0_.DATE_OUVERTURE_PLIS>'2015-01-01'
and (appeloffre0_.CATEGORIE='fournitures' or appeloffre0_.CATEGORIE='travaux' or appeloffre0_.CATEGORIE='services')
and acheteur1_.ID_ENTITE_MERE=2
解释cmd：
+----+--------------------+--------------+------+---------------------------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------------+--------------+------+---------------------------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
| 1 | PRIMARY | acheteur1_ | ref | PRIMARY,acheteur_ibfk_1 | acheteur_ibfk_1 | 5 | const | 3 | Using where; Using index |
| 1 | PRIMARY | appeloffre0_ | ref | appel_offre_ibfk_2 | appel_offre_ibfk_2 | 4 | ao.acheteur1_.ID_ACHETEUR | 31061 | Using where |
| 4 | DEPENDENT SUBQUERY | aoactivite4_ | ref | ao_activites_activite_fk,ao_activites_ao_fk | ao_activites_ao_fk | 4 | ao.appeloffre0_.ID_APPEL_OFFRE | 3 | Using where |
| 3 | DEPENDENT SUBQUERY | lieuexecut3_ | ref | fk_ao_lieuex,fk_region_lieuex | fk_ao_lieuex | 4 | ao.appeloffre0_.ID_APPEL_OFFRE | 1 | Using where |
| 2 | DEPENDENT SUBQUERY | lot2_ | ref | FK_LOT_AO | FK_LOT_AO | 4 | ao.appeloffre0_.ID_APPEL_OFFRE | 5 | Using where |
+----+--------------------+--------------+------+---------------------------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
索引acheteur_ibfk_1是FK引用表ENTITE_MERE，因为我在where子句中有acheteur1_.ID_ENTITE_MERE=2。
答案 0 :(得分：1)
通过使用ON condition1 AND condition2等，您可以在joins上拥有多个条件。
SELECT COUNT(appeloffre0_.ID_APPEL_OFFRE) as size
FROM ao.appel_offre appeloffre0_
JOIN ao.acheteur acheteur1_ ON appeloffre0_.ID_ACHETEUR=acheteur1_.ID_ACHETEUR
JOIN ao.lot lot2_ ON appeloffre0_.ID_APPEL_OFFRE=lot2_.ID_APPEL_OFFRE AND lot2_.ESTIMATION_COUT>=1
JOIN ao.lieu_execution lieuexecut3_ ON appeloffre0_.ID_APPEL_OFFRE=lieuexecut3_.ID_APPEL_OFFRE AND lieuexecut3_.ID_ACTIVITE=1
JOIN ao.ao_activite aoactivite4_ ON appeloffre0_.ID_APPEL_OFFRE=aoactivite4_.ID_APPEL_OFFRE AND aoactivite4_.ID_ACTIVITE=1
WHERE appeloffre0_.DATE_OUVERTURE_PLIS>'2015-01-01'
AND (appeloffre0_.CATEGORIE='fournitures' OR appeloffre0_.CATEGORIE='travaux' OR appeloffre0_.CATEGORIE='services')
AND acheteur1_.ID_ENTITE_MERE=2;
答案 1 :(得分：1)
您可以尝试：
select count(aa.ID_APPEL_OFFRE) as size
from (
select ID_APPEL_OFFRE, ID_ACHETEUR from ao.appel_offre appeloffre0_
inner join ao.acheteur acheteur1_
on appeloffre0_.ID_ACHETEUR=acheteur1_.ID_ACHETEUR
where appeloffre0_.DATE_OUVERTURE_PLIS>'2015-01-01'
and (appeloffre0_.CATEGORIE in ('fournitures','travaux','services'))
and (acheteur1_.ID_ENTITE_MERE=2)) aa
inner join ao.lot lot2_ on lot2_.ID_APPEL_OFFRE=aa.ID_APPEL_OFFRE
inner join ao.lieu_execution lieuexecut3_ on lieuexecut3_.appel_offre=aa.ID_APPEL_OFFRE
inner join ao.ao_activite aoactivite4_ on aoactivite4_.ID_APPEL_OFFRE=aa.ID_APPEL_OFFRE
where
aoactivite4_.ID_ACTIVITE=1
and lot2_.ESTIMATION_COUT>=1
and lieuexecut3_.region=1;
但是我没有看到你的牌桌，所以我不能100％确定你不会因为连接而得到重复。
通过确保你的appeloffre0_.CATEGORIE和appeloffre0_.DATE_OUVERTURE_PLIS上有索引，也可以找到一些低调的成果。
其他应该有索引的字段是ao.lot.ID_APPEL_OFFRE，ao.lieu_execution.ID_APPEL_OFFRE和ao.ao_activite.ID_APPEL_OFFRE，以及ao.appel_offre.ID_ACHETEUR（所有已连接的字段）。
答案 2 :(得分：1)
如果还没有，我的表上会有以下索引......这些索引覆盖了查询的索引，这意味着索引具有适用的列，无需转到实际的原始数据页即可获得结果。
table index
appel_offre ( DATE_OUVERTURE_PLIS, CATEGORIE, ID_APPEL_OFFRE, ID_ACHETEUR )
lot ( ID_APPEL_OFFRE, ESTIMATION_COUT )
lieu_execution ( appel_offre, region )
ao_activite ( ID_APPEL_OFFRE, ID_ACTIVITE )
仅在单个列上建立索引并不能真正帮助优化您要查找的内容。此外，我正在计算DISTINCT ID_APPEL_OFFRE，以防任何JOINed表有超过1条记录，它不会为您创建笛卡尔结果计数
select
count(distinct AOF.ID_APPEL_OFFRE) as size
from
ao.appel_offre AOF
JOIN ao.acheteur ACH
on AOF.ID_ACHETEUR = ACH.ID_ACHETEUR
and ACH.ID_ENTITE_MERE = 2
JOIN ao.lot
ON AOF.ID_APPEL_OFFRE = lot.ID_APPEL_OFFRE
and lot.ESTIMATION_COUT >= 1
JOIN ao.lieu_execution EX
ON AOF.ID_APPEL_OFFRE = EX.appel_offre
and EX.region = 1
JOIN ao.ao_activite ACT
ON AOF.ID_APPEL_OFFRE = ACT.ID_APPEL_OFFRE
and ACT.ID_ACTIVITE = 1
where
AOF.DATE_OUVERTURE_PLIS > '2015-01-01'
and ( AOF.CATEGORIE = 'fournitures'
or AOF.CATEGORIE = 'travaux'
or AOF.CATEGORIE = 'services')
答案 3 :(得分：0)
就像@FuzzyTree在他的评论exists中说的那样，如果它不是1：1关系，则比内连接更快，因为它一找到1就会终止，而连接将获得每个匹配的行。
但解决方法是我们添加in而不是exists：
where ( appeloffre0_.ID_APPEL_OFFRE IN (select lot2_.ID_APPEL_OFFRE from ao.lot lot2_
where lot2_.ESTIMATION_COUT>=1)
)
因此查询运行速度比存在或加入速度快。
select count(appeloffre0_.ID_APPEL_OFFRE) as size
from ao.appel_offre appeloffre0_
inner join ao.acheteur acheteur1_
on appeloffre0_.ID_ACHETEUR=acheteur1_.ID_ACHETEUR
where
( appeloffre0_.ID_APPEL_OFFRE IN (select lot2_.ID_APPEL_OFFRE from ao.lot lot2_ where lot2_.ESTIMATION_COUT>=1))
and (appeloffre0_.ID_APPEL_OFFRE IN (select lieuexecut3_.appel_offre from ao.lieu_execution lieuexecut3_ where lieuexecut3_.region=1))
and (appeloffre0_.ID_APPEL_OFFRE IN (select aoactivite4_.ID_APPEL_OFFRE from ao.ao_activite aoactivite4_ where aoactivite4_.ID_ACTIVITE=1 ))
and appeloffre0_.DATE_OUVERTURE_PLIS>'2015-01-01'
and (appeloffre0_.CATEGORIE='fournitures' or appeloffre0_.CATEGORIE='travaux' or appeloffre0_.CATEGORIE='services')
and acheteur1_.ID_ENTITE_MERE=2