Mysql 计数查询需要很多时间
我的数据库Mysql 计数查询需要很多时间,mysql,sql,Mysql,Sql,我的数据库mysql中有61K行,我试图进行计数,但查询需要4秒钟,我觉得太多了 select count( distinct appeloffre0_.ID_APPEL_OFFRE) from ao.appel_offre appeloffre0_ inner join ao.lot lots1_ on appeloffre0_.ID_APPEL_OFFRE=lots1_.ID_APPEL_OFFRE inner join ao.lieu_execution lieuexecut2_ o
mysql
中有61K行,我试图进行计数,但查询需要4秒钟,我觉得太多了
select count( distinct appeloffre0_.ID_APPEL_OFFRE)
from ao.appel_offre appeloffre0_
inner join ao.lot lots1_ on appeloffre0_.ID_APPEL_OFFRE=lots1_.ID_APPEL_OFFRE
inner join ao.lieu_execution lieuexecut2_ on appeloffre0_.ID_APPEL_OFFRE=lieuexecut2_.appel_offre
inner join ao.acheteur acheteur3_ on appeloffre0_.ID_ACHETEUR=acheteur3_.ID_ACHETEUR
inner join ao.ao_activite aoactivite4_ on appeloffre0_.ID_APPEL_OFFRE=aoactivite4_.ID_APPEL_OFFRE
我的查询结果:
+----------------------------------------------+
| count( distinct appeloffre0_.ID_APPEL_OFFRE) |
+----------------------------------------------+
| 61100 |
+----------------------------------------------+
1 row in set (4.35 sec)
为什么在explain
cmd表appeloffre0
中使用键appel\u offre\u ibfk\u 2
,它是FK列ID\u acheer
上的索引
+----+-------------+--------------+--------+----------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+--------+----------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
| 1 | SIMPLE | appeloffre0_ | index | PRIMARY,appel_offre_ibfk_2 | appel_offre_ibfk_2 | 4 | NULL | 60031 | Using index |
| 1 | SIMPLE | acheteur3_ | eq_ref | PRIMARY | PRIMARY | 4 | ao.appeloffre0_.ID_ACHETEUR | 1 | Using index |
| 1 | SIMPLE | lieuexecut2_ | ref | fk_ao_lieuex | fk_ao_lieuex | 4 | ao.appeloffre0_.ID_APPEL_OFFRE | 1 | Using index |
| 1 | SIMPLE | aoactivite4_ | ref | ao_activites_ao_fk | ao_activites_ao_fk | 4 | ao.lieuexecut2_.appel_offre | 3 | Using where; Using index |
| 1 | SIMPLE | lots1_ | ref | FK_LOT_AO | FK_LOT_AO | 4 | ao.lieuexecut2_.appel_offre | 5 | Using where; Using index |
+----+-------------+--------------+--------+----------------------------+--------------------+---------+--------------------------------+-------+--------------------------+
5 rows in set (0.00 sec)
显示来自appel_offre的索引
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| appel_offre | 0 | PRIMARY | 1 | ID_APPEL_OFFRE | A | 60953 | NULL | NULL | | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_1 | 1 | ID_APPEL_OFFRE_MERE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_2 | 1 | ID_ACHETEUR | A | 2 | NULL | NULL | | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_3 | 1 | USER_SAISIE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_4 | 1 | USER_VALIDATION | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | ao_fk_3 | 1 | TYPE_MARCHE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | ao_fk_5 | 1 | USER_CONTROLE | A | 2 | NULL | NULL | YES | BTREE | | |
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
7 rows in set (0.03 sec)
不要在计数中使用
distinct
,而是尝试用exists
条件替换1对多的内部联接
例如,如果lot.ID\u APPEL\u OFFRE
不是唯一的,则删除内部联接
inner join ao.lot lots1_ on appeloffre0_.ID_APPEL_OFFRE=lots1_.ID_APPEL_OFFRE
并在where子句中添加exists条件
where exists (select 1 from ao.lot lots_1 where appeloffre0_.ID_APPEL_OFFRE=lots1_.ID_APPEL_OFFRE)
谢谢@FuzzyTree它将我的时间缩短到0.7秒,你能回答我的2分和3分吗?因为我将使用具有多个联接的多条件搜索。如果可以的话,你可以给我一首很好的图图。@Youssef根据你的解释输出,看起来你已经在多重连接/where标准中正确地使用了索引。似乎在添加了一些where子句之后,又花了一段时间来检查这里