我有这样的查询：
SELECT DISTINCT devices1_.id AS id27_, devices1_.createdTime AS createdT2_27_, devices1_.deletedOn AS deletedOn27_,
devices1_.deviceAlias AS deviceAl4_27_, devices1_.deviceName AS deviceName27_, devices1_.deviceTypeId AS deviceT21_27_,
devices1_.equipmentVendor AS equipmen6_27_, devices1_.exceptionDetail AS exceptio7_27_, devices1_.hardwareVersion AS hardware8_27_,
devices1_.ipAddress AS ipAddress27_, devices1_.isDeleted AS isDeleted27_, devices1_.loopBack AS loopBack27_,
devices1_.modifiedTime AS modifie12_27_, devices1_.osVersion AS osVersion27_, devices1_.productModel AS product14_27_,
devices1_.productName AS product15_27_, devices1_.routerType AS routerType27_, devices1_.rundate AS rundate27_,
devices1_.serialNumber AS serialN18_27_, devices1_.serviceName AS service19_27_, devices1_.siteId AS siteId27_,
devices1_.siteIdA AS siteIdA27_, devices1_.status AS status27_, devices1_.creator AS creator27_, devices1_.lastModifier AS lastMod25_27_
FROM goldenvariation goldenconf0_
INNER JOIN devices devices1_ ON goldenconf0_.deviceId=devices1_.id
CROSS JOIN devices devices2_
WHERE goldenconf0_.deviceId=devices2_.id
AND (goldenconf0_.classType = 'policy-options')
AND DATE(goldenconf0_.rundate)=DATE('2014-04-14 00:00:00')
AND devices2_.isDeleted=0
AND EXISTS (SELECT DISTINCT(deviceId) FROM goldenvariation goldenconf3_
WHERE (goldenconf3_.goldenVariationType = 'MISMATCH')
AND (goldenconf3_.classType = 'policy-options')
AND DATE(goldenconf3_.rundate)=DATE('2014-04-14 00:00:00'))
AND EXISTS (SELECT DISTINCT (deviceId) FROM goldenvariation goldenconf4_
WHERE (goldenconf4_.goldenVariationType = 'MISSING')
AND (goldenconf4_.classType = 'policy-options')
AND DATE(goldenconf4_.rundate)=DATE('2014-04-14 00:00:00'));
它花了太多时间，我如何重写查询并快速完成？
goldervariation的表结构是：
CREATE TABLE `goldenvariation` (
`id` BIGINT(20) NOT NULL AUTO_INCREMENT,
`classType` VARCHAR(255) DEFAULT NULL,
`createdTime` DATETIME DEFAULT NULL,
`goldenValue` LONGTEXT,
`goldenXpath` VARCHAR(255) DEFAULT NULL,
`isMatched` TINYINT(1) DEFAULT NULL,
`modifiedTime` DATETIME DEFAULT NULL,
`pathValue` LONGTEXT,
`rundate` DATETIME DEFAULT NULL,
`value` LONGTEXT,
`xpath` VARCHAR(255) DEFAULT NULL,
`deviceId` BIGINT(20) DEFAULT NULL,
`goldenXpathId` BIGINT(20) DEFAULT NULL,
`creator` INT(10) UNSIGNED DEFAULT NULL,
`lastModifier` INT(10) UNSIGNED DEFAULT NULL,
`goldenVariationType` VARCHAR(255) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `FK6804472AD99F2D15` (`deviceId`),
KEY `FK6804472A98002838` (`goldenXpathId`),
KEY `FK6804472A27C863B` (`creator`),
KEY `FK6804472A3617A57C` (`lastModifier`),
KEY `rundateindex` (`rundate`),
KEY `varitionidindex` (`id`),
KEY `classTypeindex` (`classType`),
CONSTRAINT `FK6804472A27C863B` FOREIGN KEY (`creator`) REFERENCES `users` (`userid`),
CONSTRAINT `FK6804472A3617A57C` FOREIGN KEY (`lastModifier`) REFERENCES `users` (`userid`),
CONSTRAINT `FK6804472A98002838` FOREIGN KEY (`goldenXpathId`) REFERENCES `goldenconfigurationxpath` (`id`),
CONSTRAINT `FK6804472AD99F2D15` FOREIGN KEY (`deviceId`) REFERENCES `devices` (`id`)
) ENGINE=INNODB AUTO_INCREMENT=1868865 DEFAULT CHARSET=latin1;
解释查询计划是：
"1" "PRIMARY" "goldenconf0_" "ref" "FK6804472AD99F2D15,classTypeindex" "classTypeindex" "258" "const" "179223" "Using where; Using temporary"
"1" "PRIMARY" "devices2_" "eq_ref" "PRIMARY,deviceindex" "PRIMARY" "8" "cmdb.goldenconf0_.deviceId" "1" "Using where"
"1" "PRIMARY" "devices1_" "eq_ref" "PRIMARY,deviceindex" "PRIMARY" "8" "cmdb.goldenconf0_.deviceId" "1" ""
"3" "DEPENDENT SUBQUERY" "goldenconf4_" "index_subquery" "FK6804472AD99F2D15,classTypeindex" "FK6804472AD99F2D15" "9" "func" "19795" "Using where"
"2" "DEPENDENT SUBQUERY" "goldenconf3_" "index_subquery" "FK6804472AD99F2D15,classTypeindex" "FK6804472AD99F2D15" "9" "func" "19795" "Using where"
答案 0 :(得分：1)
INNER JOIN goldenvariation goldenconf4_
ON goldenconf4_.deviceId = goldenconf0_deviceId
AND (goldenconf4_.goldenVariationType = 'MISSING')
AND (goldenconf4_.classType = 'policy-options')
AND DATE(goldenconf4_.rundate)=DATE('2014-04-14 00:00:00'))
以同样的方式更改另一个EXISTS。我认为这个应该更快。我也是小小的提示：尝试使用较短的别名。您的查询真的很难读。
SELECT DISTINCT
devices1_.id AS id27_,
devices1_.createdTime AS createdT2_27_,
devices1_.deletedOn AS deletedOn27_,
devices1_.deviceAlias AS deviceAl4_27_,
devices1_.deviceName AS deviceName27_,
devices1_.deviceTypeId AS deviceT21_27_,
devices1_.equipmentVendor AS equipmen6_27_,
devices1_.exceptionDetail AS exceptio7_27_,
devices1_.hardwareVersion AS hardware8_27_,
devices1_.ipAddress AS ipAddress27_,
devices1_.isDeleted AS isDeleted27_,
devices1_.loopBack AS loopBack27_,
devices1_.modifiedTime AS modifie12_27_,
devices1_.osVersion AS osVersion27_,
devices1_.productModel AS product14_27_,
devices1_.productName AS product15_27_,
devices1_.routerType AS routerType27_,
devices1_.rundate AS rundate27_,
devices1_.serialNumber AS serialN18_27_,
devices1_.serviceName AS service19_27_,
devices1_.siteId AS siteId27_,
devices1_.siteIdA AS siteIdA27_,
devices1_.status AS status27_,
devices1_.creator AS creator27_,
devices1_.lastModifier AS lastMod25_27_
FROM goldenvariation goldenconf0_
INNER JOIN devices devices1_ ON goldenconf0_.deviceId=devices1_.id
INNER JOIN goldenvariation a on a.deviceId = goldenconf0_.deviceId and a.goldenVariationType = 'MISMATCH'
INNER JOIN goldenvariation b on b.deviceId = goldenconf0_.deviceId and b.goldenVariationType = 'MISSING'
WHERE (goldenconf0_.classType = 'policy-options')
AND convert(date,goldenconf0_.rundate) = '2014-04-14'
AND devices1_.isDeleted=0
试试这个。应该比你的查询更快地工作。您使用CROSS JOIN加入了表格，但SELECT中没有使用此列中的一列。
答案 1 :(得分：1)
您正在寻找通过EXISTS与黄金变化表相关联的元素。我将从该表开始获取不同的ID，然后加入您的设备表。此外，在转换日期时，您无法利用INDEX（如果是索引的一部分）。
INDEX ...（classType，rundate，goldenVariationType，deviceID）
将date子句更改为＆gt; =？和＆lt; ？+1这样，您可以获得当天凌晨12:00:00到当天晚上11:59:59的整个日期范围，索引可以使用日期组件而无需转换每条记录。
此外，您正在对匹配的＆＃34; ID＆＃34;上的设备表TWICE进行交叉连接。从goldenVariations表到相同ID的设备1和2，这是浪费而没有做任何事情。
您的设备表应具有索引ON（id，isDeleted）
SELECT
d1.id AS id27,
d1.createdTime AS createdT2_27,
d1.deletedOn AS deletedOn27,
d1.deviceAlias AS deviceAl4_27_,
d1.deviceName AS deviceName27_,
d1.deviceTypeId AS deviceT21_27_,
d1.equipmentVendor AS equipmen6_27_,
d1.exceptionDetail AS exceptio7_27_,
d1.hardwareVersion AS hardware8_27_,
d1.ipAddress AS ipAddress27_,
d1.isDeleted AS isDeleted27_,
d1.loopBack AS loopBack27_,
d1.modifiedTime AS modifie12_27_,
d1.osVersion AS osVersion27_,
d1.productModel AS product14_27_,
d1.productName AS product15_27_,
d1.routerType AS routerType27_,
d1.rundate AS rundate27_,
d1.serialNumber AS serialN18_27_,
d1.serviceName AS service19_27_,
d1.siteId AS siteId27_,
d1.siteIdA AS siteIdA27_,
d1.status AS status27_,
d1.creator AS creator27_,
d1.lastModifier AS lastMod25_27_
from
( SELECT distinct
gv.deviceID
from
goldenVariation gv
where
gv.classType = 'policy-options'
AND gv.runDate >= '2014-04-14'
AND gv.runDate < '2014-04-15'
AND gv.goldenVariationType IN ( 'MISSING', 'MISMATCH' )) PQ
JOIN devices d1
ON PQ.deviceId = d1.id
AND d1.isDeleted = 0
答案 2 :(得分：1)
是的，可以重写查询以提高性能（虽然它看起来像是由Hibernate生成的查询，并且让Hibernate使用不同的查询可能是一个挑战。）
您对此查询返回预期结果集的确定程度如何？因为查询很奇怪。
就性能，甜甜圈的美元，实际吃午餐的依赖子查询的重复执行，以及性能方面的饭盒而言。看起来MySQL正在使用 deviceId 列上的索引来满足该子查询，这看起来不是最合适的索引。
我们注意到devices表有两个JOIN操作;这个表没有理由需要连接两次。两个JOIN操作都需要与goldenvariation的deviceID列匹配，而对devices表的第二个连接需要使用isDeleted=0进行额外的过滤。关键字INNER和CROSS根本不会对声明产生任何影响;并且devices表的第二个连接实际上不是“交叉”连接，它实际上是一个内连接。 （我们更喜欢在ON子句而不是WHERE子句中看到连接谓词。
围绕DATE()列的rundate函数会禁用索引范围扫描操作。可以重写这些谓词以利用适当的索引。
EXISTS子查询的SELECT列表中的 DISTINCT(deviceId) 非常奇怪。首先，DISTINCT是关键字，而不是函数。 deviceId 周围不需要parens。但除此之外，在EXISTS子查询的SELECT列表中返回的内容无关紧要，它可能只是 SELECT 1 。
看到EXISTS谓词的查询没有引用外部查询中的任何表达式（即相关子查询），这很奇怪。这是有效的语法。使用相关子查询，MySQL对外部查询返回的每一行执行该查询。 EXPLAIN输出看起来像MySQL正在做同样的事情，它没有识别任何优化。
这些EXIST谓词的编写方式，如果没有带有'MISMATCH'的'policy-options'行，并且没有带有'MISSING'的'policy-options'行（对于指定的日期，那么查询将不返回任何行。如果找到每种类型的行（对于指定的日期，则返回该日期的所有'policy-options'行。（它在语法上有效，但它相当奇怪。）
假设devices表上的id列是UNIQUE（即它是PRIMARY KEY或该列上有UNIQUE索引，那么最外层查询上不需要DISTINCT关键字。（来自EXPLAIN输出，看起来MySQL已经优化了通常的操作，也就是说，MySQL认识到DISTINCT关键字是不必要的。
但最重要的是，它是依赖的子查询，正在扼杀性能;没有合适的索引，并且日期列中的谓词包含在函数中。
要回答您的问题，是的，可以重写此查询以更有效地返回等效的结果集。 （查询返回您期望的结果集并不完全清楚。）
SELECT d1.id AS id27_
, d1.createdTime AS createdT2_27_
, d1.deletedOn AS deletedOn27_
, d1.deviceAlias AS deviceAl4_27_
, d1.deviceName AS deviceName27_
, d1.deviceTypeId AS deviceT21_27_
, d1.equipmentVendor AS equipmen6_27_
, d1.exceptionDetail AS exceptio7_27_
, d1.hardwareVersion AS hardware8_27_
, d1.ipAddress AS ipAddress27_
, d1.isDeleted AS isDeleted27_
, d1.loopBack AS loopBack27_
, d1.modifiedTime AS modifie12_27_
, d1.osVersion AS osVersion27_
, d1.productModel AS product14_27_
, d1.productName AS product15_27_
, d1.routerType AS routerType27_
, d1.rundate AS rundate27_
, d1.serialNumber AS serialN18_27_
, d1.serviceName AS service19_27_
, d1.siteId AS siteId27_
, d1.siteIdA AS siteIdA27_
, d1.status AS status27_
, d1.creator AS creator27_
, d1.lastModifier AS lastMod25_27_
FROM devices d1
JOIN (SELECT g.deviceId
FROM goldenvariation g
CROSS
JOIN (SELECT 1
FROM goldenvariation x3
WHERE x3.goldenVariationType = 'MISMATCH'
AND x3.classType = 'policy-options'
AND x3.rundate >= '2014-04-14'
AND x3.rundate < '2014-04-14' + INTERVAL 1 DAY
LIMIT 1
) t3
CROSS
JOIN (SELECT 1
FROM goldenvariation x4
WHERE x4.goldenVariationType = 'MISSING'
AND x4.classType = 'policy-options'
AND x4.rundate >= '2014-04-14'
AND x4.rundate < '2014-04-14' + INTERVAL 1 DAY
LIMIT 1
) t4
WHERE g.classType = 'policy-options'
AND g.rundate >= '2014-04-14'
AND g.rundate < '2014-04-14' + INTERVAL 1 DAY
GROUP BY g.deviceId
) t2
ON t2.device_id = d1.id
WHERE d1.isDeleted=0