Mysql 如何跨三个联接的表提高不同选择的性能？

我有以下表格：

人物角色 ImpressionPersonas[加入表格-角色众多印象] 印象 我的查询如下所示，解释结果附在下面：

   SELECT

   DISTINCT (Personas.id),
    Personas.parent_id, 
   Personas.persona, 
   Personas.subpersonas_count, 
   Personas.is_subpersona, 
   Personas.impressions_count, 
   Personas.created, 
   Personas.modified


   FROM personas as Personas 

   INNER JOIN   
        impressions_personas ImpressionsPersonas ON (
        Personas.id = ImpressionsPersonas.persona_id
    )
   inner JOIN impressions Impressions ON (Impressions.id = ImpressionsPersonas.impression_id AND Impressions.timestamp >= "2016-06-01 00:00:00" AND Impressions.timestamp <= "2016-07-31 00:00:00") 

为角色创建语句

为印象和人物角色创建语句

为印象创建语句

现在-当我在不使用DISTINCT并使用COUNT*的情况下运行查询时，它会提取大约17000000条记录。使用不同的记录运行它可以产生112条记录。我不知道为什么会有这么多的记录出现，而解释显示只有159和396条

有关表格的一些信息：

Personas表包含159条记录。ImpressionPersonas表包含大约1260万条记录，Impressions包含大约920000条记录

我们正在做的是选择Personas表并通过连接表impressionsponas连接到印象。在这种情况下，存在应用于Impressions表日期的过滤器

注意：删除日期过滤器对执行时间的影响可以忽略不计，执行时间大约在120秒左右。有没有办法过滤这些记录以缩短此查询的执行时间？

在impressions表的timestamp列上创建索引。并查看是否尝试在queryforcing索引中使用创建的索引

更新

在联接中使用索引

---

我假设您希望获得在指定时间段内至少有1个印象的人员列表。要获得此信息，您可以使用这样一个相关子查询：

SELECT
   Personas.id,
   Personas.parent_id, 
   Personas.persona, 
   Personas.subpersonas_count, 
   Personas.is_subpersona, 
   Personas.impressions_count, 
   Personas.created, 
   Personas.modified

   FROM personas as Personas 
   WHERE EXISTS(SELECT 1 FROM impressions_personas 
       LEFT JOIN impressions Impressions ON 
           Impressions.id = ImpressionsPersonas.impression_id 
       WHERE Personas.id = ImpressionsPersonas.persona_id
           AND Impressions.timestamp >= "2016-06-01 00:00:00" 
           AND Impressions.timestamp <= "2016-07-31 00:00:00"
   )

---

目前，您首先要连接三个具有数百万行的表，然后使用DISTINCT只从中获取几行。更好的方法是首先只获取所需的ID，然后使用这些ID来选择实际的结果数据

例如：

SELECT column, other FROM personas
WHERE id IN
  (SELECT distinct persona_id
    FROM impressions_personas
    INNER JOIN impressions Impressions
      ON Impressions.id = ImpressionsPersonas.impression_id
        AND Impressions.timestamp >= "2016-06-01 00:00:00"
        AND Impressions.timestamp <= "2016-07-31 00:00:00"))

---

这样，引擎将只处理整个过程中的一个列，直到得到结果。

将整个连接更改为IN或其他帮助吗？不确定引擎是如何处理事情的，但当你实际上只是在寻找唯一的id，然后从personas表中获取这些记录时，连接和区分似乎有点毫无意义Impressions.id=ImpressionPersonas.impression\u id AND Impressions.timestamp>=2016-06-01 00:00:00 AND Impressions.timestamp@SamiKuhmonen well-由于存在联接表，因此会返回重复的记录，因此需要进行不同的选择。@BarryChapman是，但是，当您首先执行distinct/group by，然后选择所需的实际行时，可能会有很大的不同。您不需要连接三个表，只需连接两个表，就可以获得几个ID来选择最终结果。DISTINCT不是一个函数。这不需要争论。你的括号除了混淆时间戳之外没有任何作用，

CREATE TABLE `impressions_personas` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `impression_id` bigint(20) unsigned NOT NULL,
  `persona_id` bigint(20) unsigned NOT NULL,
  `created` datetime DEFAULT NULL,
  `modified` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `impression_idx` (`impression_id`),
  KEY `persona_idx` (`persona_id`),
  KEY `comp_imp_persona` (`impression_id`,`persona_id`),
  KEY `comp_imp_pri` (`impression_id`,`id`),
  KEY `comp_per_pri` (`persona_id`,`id`),
  CONSTRAINT `impression` FOREIGN KEY (`impression_id`) REFERENCES `impressions` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION,
  CONSTRAINT `persona` FOREIGN KEY (`persona_id`) REFERENCES `personas` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=19387839 DEFAULT CHARSET=utf8;

CREATE TABLE `impressions` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `device_id` bigint(20) unsigned NOT NULL,
  `beacon_id` bigint(20) unsigned NOT NULL,
  `zone_id` bigint(20) unsigned NOT NULL,
  `application_id` bigint(20) unsigned DEFAULT NULL,
  `timestamp` datetime NOT NULL,
  `google_place_id` bigint(20) unsigned DEFAULT NULL,
  `name` varchar(60) DEFAULT NULL,
  `lat` decimal(15,10) DEFAULT NULL,
  `lng` decimal(15,10) DEFAULT NULL,
  `personas_count` int(10) unsigned DEFAULT '0',
  `created` datetime DEFAULT NULL,
  `modified` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `device_idx` (`device_id`),
  KEY `zone_idx` (`zone_id`),
  KEY `beacon_id_idx2` (`beacon_id`),
  KEY `timestamp` (`timestamp`),
  KEY `appid_fk_idx_idx` (`application_id`),
  KEY `comp_lookup` (`device_id`,`beacon_id`,`timestamp`),
  KEY `timestamp_id` (`timestamp`,`id`),
  CONSTRAINT `appid_fk_idx` FOREIGN KEY (`application_id`) REFERENCES `applications` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `beacon_id` FOREIGN KEY (`beacon_id`) REFERENCES `beacons` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION,
  CONSTRAINT `device2` FOREIGN KEY (`device_id`) REFERENCES `devices` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `zone_FK` FOREIGN KEY (`zone_id`) REFERENCES `zones` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=1582724 DEFAULT CHARSET=utf8;

SELECT
DISTINCT (Personas.id),
Personas.parent_id, 
Personas.persona, 
Personas.subpersonas_count, 
Personas.is_subpersona, 
Personas.impressions_count, 
Personas.created, 
Personas.modified
FROM 
    personas as Personas 
INNER JOIN   
    impressions_personas ImpressionsPersonas ON (
    Personas.id = ImpressionsPersonas.persona_id
)
INNER JOIN 
    impressions Impressions WITH(INDEX(timestamp)) ON 
    (Impressions.id = ImpressionsPersonas.impression_id AND
    Impressions.timestamp >= "2016-06-01 00:00:00" AND 
    Impressions.timestamp <= "2016-07-31 11:59:59")  

SELECT
   Personas.id,
   Personas.parent_id, 
   Personas.persona, 
   Personas.subpersonas_count, 
   Personas.is_subpersona, 
   Personas.impressions_count, 
   Personas.created, 
   Personas.modified

   FROM personas as Personas 
   WHERE EXISTS(SELECT 1 FROM impressions_personas 
       LEFT JOIN impressions Impressions ON 
           Impressions.id = ImpressionsPersonas.impression_id 
       WHERE Personas.id = ImpressionsPersonas.persona_id
           AND Impressions.timestamp >= "2016-06-01 00:00:00" 
           AND Impressions.timestamp <= "2016-07-31 00:00:00"
   )

SELECT column, other FROM personas
WHERE id IN
  (SELECT distinct persona_id
    FROM impressions_personas
    INNER JOIN impressions Impressions
      ON Impressions.id = ImpressionsPersonas.impression_id
        AND Impressions.timestamp >= "2016-06-01 00:00:00"
        AND Impressions.timestamp <= "2016-07-31 00:00:00"))