我的查询运行时间超过3分钟。我希望优化在几秒钟内运行：
SELECT Count(DISTINCT l.licitatii_id) c
FROM licitatii_ue l
INNER JOIN domenii_licitatii dl
ON l.licitatii_id = dl.licitatii_id
AND dl.tip_licitatie = '2'
INNER JOIN domenii d
ON dl.domenii_id = d.domenii_id
AND d.tip_domeniu = '1'
AND d.status = 1
WHERE l.status = 1
AND l.data_limita >= '1357768800'
解释说明：
*** row 1 ***
table: d
type: ref
possible_keys: PRIMARY,key_status_tip_domeniu,ind_v1
key: key_status_tip_domeniu
key_len: 9
ref: const,const
rows: 39
Extra: Using where; Using index
*** row 2 ***
table: dl
type: ref
possible_keys: PRIMARY,licitatii_id,licitatii_id_2
key: PRIMARY
key_len: 5
ref: web1db1.d.domenii_id,const
rows: 1882
Extra: Using index
*** row 3 ***
table: l
type: eq_ref
possible_keys: PRIMARY,data_limita
key: PRIMARY
key_len: 4
ref: web1db1.dl.licitatii_id
rows: 1
Extra: Using where
架构：
licitatii_ue
PRIMARY KEY (`licitatii_id`),
UNIQUE KEY `nr_ue` (`nr_ue`),
KEY `nume` (`nume`),
KEY `tip_licitatie` (`tip_licitatie`),
KEY `surse_ue_id` (`surse_ue_id`),
KEY `data_publicarii` (`data_publicarii`),
KEY `tara_id` (`tara_id`),
KEY `creat` (`creat`),
KEY `data_limita` (`data_limita`),
FULLTEXT KEY `nume_fulltext` (`nume`,`descriere`)
) ENGINE=MyISAM
/*Index Information*/
---------------------
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
------------ ---------- --------------- ------------ --------------- --------- ----------- -------- ------ ------ ---------- ---------
licitatii_ue 0 PRIMARY 1 licitatii_id A 136456 (NULL) (NULL) BTREE
licitatii_ue 0 nr_ue 1 nr_ue A (NULL) (NULL) (NULL) YES BTREE
licitatii_ue 1 nume 1 nume A 68228 (NULL) (NULL) BTREE
licitatii_ue 1 tip_licitatie 1 tip_licitatie A 13 (NULL) (NULL) YES BTREE
licitatii_ue 1 surse_ue_id 1 surse_ue_id A 1 (NULL) (NULL) BTREE
licitatii_ue 1 data_publicarii 1 data_publicarii A 136456 (NULL) (NULL) YES BTREE
licitatii_ue 1 tara_id 1 tara_id A 41 (NULL) (NULL) YES BTREE
licitatii_ue 1 creat 1 creat A 136456 (NULL) (NULL) YES BTREE
licitatii_ue 1 data_limita 1 data_limita A 770 (NULL) (NULL) YES BTREE
licitatii_ue 1 nume_fulltext 1 nume (NULL) 1 (NULL) (NULL) FULLTEXT
licitatii_ue 1 nume_fulltext 2 descriere (NULL) 1 (NULL) (NULL) YES FULLTEXT
domenii_licitatii
PRIMARY KEY (`domenii_id`,`tip_licitatie`,`licitatii_id`),
KEY `licitatii_id` (`licitatii_id`,`tip_licitatie`),
KEY `licitatii_id_2` (`licitatii_id`)
) ENGINE=InnoDB
/*Index Information*/
---------------------
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
----------------- ---------- -------------- ------------ ------------- --------- ----------- -------- ------ ------ ---------- ---------
domenii_licitatii 0 PRIMARY 1 domenii_id A 20 (NULL) (NULL) BTREE
domenii_licitatii 0 PRIMARY 2 tip_licitatie A 228 (NULL) (NULL) BTREE
domenii_licitatii 0 PRIMARY 3 licitatii_id A 430634 (NULL) (NULL) BTREE
domenii_licitatii 1 licitatii_id 1 licitatii_id A 430634 (NULL) (NULL) BTREE
domenii_licitatii 1 licitatii_id 2 tip_licitatie A 430634 (NULL) (NULL) BTREE
domenii_licitatii 1 licitatii_id_2 1 licitatii_id A 430634 (NULL) (NULL) BTREE
domenii
PRIMARY KEY (`domenii_id`),
KEY `key_status_tip_domeniu` (`status`,`tip_domeniu`),
KEY `ind_v1` (`domenii_id`,`tip_domeniu`,`status`),
KEY `parent_id` (`parent_id`)
) ENGINE=InnoDB
/*Index Information*/
---------------------
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
------- ---------- ---------------------- ------------ ----------- --------- ----------- -------- ------ ------ ---------- ---------
domenii 0 PRIMARY 1 domenii_id A 79 (NULL) (NULL) BTREE
domenii 1 key_status_tip_domeniu 1 status A 4 (NULL) (NULL) YES BTREE
domenii 1 key_status_tip_domeniu 2 tip_domeniu A 11 (NULL) (NULL) BTREE
domenii 1 ind_v1 1 domenii_id A 79 (NULL) (NULL) BTREE
domenii 1 ind_v1 2 tip_domeniu A 79 (NULL) (NULL) BTREE
domenii 1 ind_v1 3 status A 79 (NULL) (NULL) YES BTREE
domenii 1 parent_id 1 parent_id A 79 (NULL) (NULL) BTREE
答案 0 :(得分：1)
你的桌子上确实需要复合索引。
table index
licitatii ( status, data_limita, licitatii_id )
domenii_licitatii ( licitatii_id, tip_licitatie )
domenii ( domenii_id, tip_domeniu, status )
您应该有复合键，以帮助优化您的联接和标准。另外，正如我所包含的那样，查询引擎可以直接从索引中找到联接的值，而不是返回到实际数据的页面。如果索引中只有一个列，则查询将转到要加入的原始数据。看看它为你做了什么。
好的，是的，其他两个索引和你添加了第三个 - 没有帮助。然后我会尝试将查询反转一些...不完全知道数据，但看起来它们是某种类型的查找类别元素。尝试
select STRAIGHT_JOIN
Count(DISTINCT dl.licitatii_id) c
from
domenii d
join domenii_licitatii dl
on d.domenii_id = dl.domenii_id
AND dl.tip_licitatie = '2'
JOIN licitatii_ue L
on dl.licitatii_id = L.licitatii_id
AND L.status = 1
AND L.Data_Limita >= '1357768800'
where
d.tip_domeniu = '1'
and d.status = 1
由Pentium10添加
解释如下：
+---+--------+----+--------+---------------------------------------+------------------------+---+----------------------------+------+--------------------------+
| 1 | SIMPLE | d | ref | PRIMARY,key_status_tip_domeniu,ind_v1 | key_status_tip_domeniu | 9 | const,const | 39 | Using where; Using index |
| 1 | SIMPLE | dl | ref | PRIMARY,licitatii_id,licitatii_id_2 | PRIMARY | 5 | web1db1.d.domenii_id,const | 1882 | Using index |
| 1 | SIMPLE | L | eq_ref | PRIMARY,data_limita,i1 | PRIMARY | 4 | web1db1.dl.licitatii_id | 1 | Using where |
+---+--------+----+--------+---------------------------------------+------------------------+---+----------------------------+------+--------------------------+
答案 1 :(得分：0)
这里我将最后的WHERE子句移动到开头的子查询中，因此它不必过滤最后由INNER JOIN创建的更多行，它已经是及时正确过滤了第一个INNER JOIN。这会运行2个查询，但它应该更快。
SELECT Count(DISTINCT l.licitatii_id) c
FROM (SELECT DISTINCT licitatii_id
FROM licitatii_ue l
WHERE l.status = 1
AND l.data_limita >= '1357768800'
) l
INNER JOIN domenii_licitatii dl
ON l.licitatii_id = dl.licitatii_id
AND dl.tip_licitatie = '2'
INNER JOIN domenii d
ON dl.domenii_id = d.domenii_id
AND d.tip_domeniu = '1'
AND d.status = 1