减少执行mysql查询所需的时间

时间：2012-09-21 09:47:33

标签： mysql insert query-optimization

我有两个数据库，有三个相似的表（mdl_user，mdl_course和mdl_course_enrol）。

mdl_user和mdl_course中的用户和课程的id值在两个数据库中都不同。这两个值都由第三个表引用，即mdl_course_enrol。在数据库1中，表是空的，在数据​​库2（nlbdb1_9）中，表被填充。我正在尝试执行查询，以便在mdl_course_enrol中输入正确的值。以下是我的询问： - 

Insert into mdl_course_enrol 
(userid, courseid, registrationdate, expirydate, status, startdate, enddate, roleassignmentid)
Select u1.id, c1.id, t2.registrationdate, t2.expirydate, t2.status, t2.startdate, t2.enddate, t2.roleassignmentid
from 
nlbdb1_9.mdl_course_enrol as t2, mdl_user as u1, mdl_course as c1
where 
t2.userid=(Select u1.id from nlbdb1_9.mdl_user as u2 where t2.userid=u2.id and BINARY u2.email=BINARY u1.email)
and
t2.courseid=(Select c1.id from nlbdb1_9.mdl_course as c2 where t2.courseid=c2.id and BINARY c2.fullname = BINARY c1.fullname);

以下是表结构： - 

CREATE TABLE `mdl_course_enrol` (
  `id` bigint(10) unsigned NOT NULL AUTO_INCREMENT,
  `userid` bigint(10) unsigned NOT NULL,
  `courseid` bigint(10) unsigned NOT NULL,
  `registrationdate` bigint(10) unsigned NOT NULL,
  `expirydate` bigint(10) unsigned NOT NULL,
  `status` varchar(32) NOT NULL DEFAULT 'Not Attempted',
  `startdate` bigint(10) NOT NULL,
  `enddate` bigint(10) NOT NULL,
  `roleassignmentid` bigint(10) unsigned NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=14962 DEFAULT CHARSET=utf8;


CREATE TABLE `mdl_course` (
  `id` bigint(10) NOT NULL AUTO_INCREMENT,
  `category` bigint(10) NOT NULL DEFAULT '0',
  `sortorder` bigint(10) NOT NULL DEFAULT '0',
  `fullname` varchar(254) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `shortname` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `idnumber` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `summary` longtext CHARACTER SET utf8 COLLATE utf8_unicode_ci,
  `summaryformat` tinyint(2) NOT NULL DEFAULT '0',
  `format` varchar(10) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT 'topics',
  `showgrades` tinyint(2) NOT NULL DEFAULT '1',
  `sectioncache` longtext CHARACTER SET utf8 COLLATE utf8_unicode_ci,
  `modinfo` longtext CHARACTER SET utf8 COLLATE utf8_unicode_ci,
  `newsitems` mediumint(5) NOT NULL DEFAULT '1',
  `startdate` bigint(10) NOT NULL DEFAULT '0',
  `numsections` mediumint(5) NOT NULL DEFAULT '1',
  `marker` bigint(10) NOT NULL DEFAULT '0',
  `maxbytes` bigint(10) NOT NULL DEFAULT '0',
  `legacyfiles` smallint(4) NOT NULL DEFAULT '0',
  `showreports` smallint(4) NOT NULL DEFAULT '0',
  `visible` tinyint(1) NOT NULL DEFAULT '1',
  `visibleold` tinyint(1) NOT NULL DEFAULT '1',
  `hiddensections` tinyint(2) NOT NULL DEFAULT '0',
  `groupmode` smallint(4) NOT NULL DEFAULT '0',
  `groupmodeforce` smallint(4) NOT NULL DEFAULT '0',
  `defaultgroupingid` bigint(10) NOT NULL DEFAULT '0',
  `lang` varchar(30) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `theme` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `timecreated` bigint(10) NOT NULL DEFAULT '0',
  `timemodified` bigint(10) NOT NULL DEFAULT '0',
  `requested` tinyint(1) NOT NULL DEFAULT '0',
  `enablecompletion` tinyint(1) NOT NULL DEFAULT '0',
  `completionstartonenrol` tinyint(1) NOT NULL DEFAULT '0',
  `completionnotify` tinyint(1) NOT NULL DEFAULT '0',
  `coursedisplay` tinyint(2) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`),
  KEY `mdl_cour_cat_ix` (`category`),
  KEY `mdl_cour_idn_ix` (`idnumber`),
  KEY `mdl_cour_sho_ix` (`shortname`),
  KEY `mdl_cour_sor_ix` (`sortorder`)
) ENGINE=InnoDB AUTO_INCREMENT=45 DEFAULT CHARSET=utf8 COMMENT='Central course table';

CREATE TABLE `mdl_user` (
  `id` bigint(10) unsigned NOT NULL AUTO_INCREMENT,
  `auth` varchar(20) NOT NULL DEFAULT 'manual',
  `confirmed` tinyint(1) NOT NULL DEFAULT '0',
  `policyagreed` tinyint(1) NOT NULL DEFAULT '0',
  `deleted` tinyint(1) NOT NULL DEFAULT '0',
  `mnethostid` bigint(10) unsigned NOT NULL DEFAULT '0',
  `username` varchar(100) NOT NULL DEFAULT '',
  `password` varchar(32) NOT NULL DEFAULT '',
  `pwdlastchange` bigint(10) unsigned NOT NULL DEFAULT '0',
  `idnumber` varchar(255) NOT NULL DEFAULT '',
  `firstname` varchar(100) NOT NULL DEFAULT '',
  `lastname` varchar(100) NOT NULL DEFAULT '',
  `email` varchar(100) NOT NULL DEFAULT '',
  `emailstop` tinyint(1) unsigned NOT NULL DEFAULT '0',
  `nric` varchar(15) NOT NULL DEFAULT '',
  `skype` varchar(50) NOT NULL DEFAULT '',
  `yahoo` varchar(50) NOT NULL DEFAULT '',
  `aim` varchar(50) NOT NULL DEFAULT '',
  `msn` varchar(50) NOT NULL DEFAULT '',
  `phone1` varchar(20) NOT NULL DEFAULT '',
  `phone2` varchar(20) NOT NULL DEFAULT '',
  `institution` varchar(40) NOT NULL DEFAULT '',
  `department` varchar(30) NOT NULL DEFAULT '',
  `address` varchar(70) NOT NULL DEFAULT '',
  `city` varchar(20) NOT NULL DEFAULT '',
  `country` varchar(2) NOT NULL DEFAULT '',
  `lang` varchar(30) NOT NULL DEFAULT 'en_utf8',
  `theme` varchar(50) NOT NULL DEFAULT '',
  `timezone` varchar(100) NOT NULL DEFAULT '99',
  `firstaccess` bigint(10) unsigned NOT NULL DEFAULT '0',
  `lastaccess` bigint(10) unsigned NOT NULL DEFAULT '0',
  `lastlogin` bigint(10) unsigned NOT NULL DEFAULT '0',
  `currentlogin` bigint(10) unsigned NOT NULL DEFAULT '0',
  `lastip` varchar(15) NOT NULL DEFAULT '',
  `secret` varchar(15) NOT NULL DEFAULT '',
  `picture` tinyint(1) NOT NULL DEFAULT '0',
  `url` varchar(255) NOT NULL DEFAULT '',
  `description` text,
  `mailformat` tinyint(1) unsigned NOT NULL DEFAULT '1',
  `maildigest` tinyint(1) unsigned NOT NULL DEFAULT '0',
  `maildisplay` tinyint(2) unsigned NOT NULL DEFAULT '2',
  `htmleditor` tinyint(1) unsigned NOT NULL DEFAULT '1',
  `ajax` tinyint(1) unsigned NOT NULL DEFAULT '1',
  `autosubscribe` tinyint(1) unsigned NOT NULL DEFAULT '1',
  `trackforums` tinyint(1) unsigned NOT NULL DEFAULT '0',
  `timemodified` bigint(10) unsigned NOT NULL DEFAULT '0',
  `trustbitmask` bigint(10) unsigned NOT NULL DEFAULT '0',
  `imagealt` varchar(255) DEFAULT NULL,
  `screenreader` tinyint(1) NOT NULL DEFAULT '0',
  `nlbid` bigint(10) unsigned DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `mdl_user_mneuse_uix` (`mnethostid`,`username`),
  KEY `mdl_user_del_ix` (`deleted`),
  KEY `mdl_user_con_ix` (`confirmed`),
  KEY `mdl_user_fir_ix` (`firstname`),
  KEY `mdl_user_las_ix` (`lastname`),
  KEY `mdl_user_cit_ix` (`city`),
  KEY `mdl_user_cou_ix` (`country`),
  KEY `mdl_user_las2_ix` (`lastaccess`),
  KEY `mdl_user_ema_ix` (`email`),
  KEY `mdl_user_aut_ix` (`auth`),
  KEY `mdl_user_idn_ix` (`idnumber`)
) ENGINE=MyISAM AUTO_INCREMENT=5902 DEFAULT CHARSET=utf8 COMMENT='One record for each person';

我正在尝试运行插入查询，但它花了太长时间。有没有办法减少时间？

以下是解释选择后的输出： -

enter image description here

1 个答案:

答案 0 :(得分：0)

我不能保证这会更快。但是，我猜这个问题出现在相关的子查询中。您可以通过运行仅选择部分来验证这一点，以查看它是否在合理的时间内运行。

此版本将相关子查询重写为连接：

Insert into mdl_course_enrol(userid, courseid, registrationdate, expirydate, status,
                             startdate, enddate, roleassignmentid)
    Select u.id, c.id, t2.registrationdate, t2.expirydate, t2.status, t2.startdate,
           t2.enddate, t2.roleassignmentid
    from nlbdb1_9.mdl_course_enrol t2 join
         nlbdb1_9.mdl_user u2
         on t2.userid = u2.userid join
         mdl_user u
         on (u.email collate utf8_unicode_ci = u2.email collate utf8_unicode_ci)  join
         nlbdb1_9.mdl_course c2
         on t2.courseid=c2.id join
         mdl_course c
         on (c2.fullname collate utf8_unicode_ci = c.fullname collate utf8_unicode_ci )
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