“优化MySQL”；在；选择？_Mysql_Database

“优化MySQL”；在；选择？

mysql database

“优化MySQL”；在；选择？,mysql,database,Mysql,Database,我有以下MySQL查询： SELECT `influencers`.*, `locations`.`country_name` FROM `influencers` LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id` WHERE `is_dead` = 0 AND `influencers`.`is_private` = 0 AND `influenc

我有以下MySQL查询：

SELECT
    `influencers`.*,
    `locations`.`country_name`
FROM
    `influencers`
    LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id`
WHERE
    `is_dead` = 0
    AND `influencers`.`is_private` = 0
    AND `influencers`.`country_id` = '31'
    AND influencers.uuid IN(
        SELECT
            `influencer_uuid` FROM `category_influencer`
        WHERE
            `category_influencer`.`category_id` = 17
            AND `category_influencer`.`is_main` = 1)
ORDER BY
    `influencers`.`followed_by` DESC
LIMIT 7 OFFSET 6

我已经确定IN子查询导致完成此查询的延迟约为10秒。下面是解释：

我在所有被查询的列上都有索引

如何显著加快查询速度？

更新为

SHOW CREATE TABLE

：

位置

CREATE TABLE `locations` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `country_name` varchar(255) DEFAULT NULL,
    `city_name` varchar(255) DEFAULT NULL,
    `type` varchar(255) DEFAULT NULL,
    PRIMARY KEY (`id`),
    UNIQUE KEY `unique_index` (`city_name`, `country_name`),
    KEY `type` (`type`)
    USING BTREE) ENGINE = InnoDB AUTO_INCREMENT = 6479 DEFAULT CHARSET = utf8mb4

CREATE TABLE `influencers` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `bio` varchar(255) CHARACTER
    SET utf8mb4 DEFAULT NULL,
    `url` varchar(255) CHARACTER
    SET utf8mb4 DEFAULT NULL,
    `followed_by` int(11) DEFAULT NULL,
    `follows` int(11) DEFAULT NULL,
    `full_name` varchar(255) CHARACTER
    SET utf8mb4 NOT NULL,
    `social_id` varchar(255) DEFAULT NULL,
    `is_private` tinyint (1) DEFAULT NULL,
    `avatar` varchar(255) NOT NULL,
    `username` varchar(30) NOT NULL,
    `text_search` text CHARACTER
    SET utf8mb4 NOT NULL,
    `updated_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
    `uuid` varchar(255) DEFAULT NULL,
    `is_dead` tinyint (4) DEFAULT NULL,
    `country_id` int(11) DEFAULT NULL,
    `city_id` int(11) DEFAULT NULL,
    PRIMARY KEY (`id`),
    UNIQUE KEY `username` (`username`),
    UNIQUE KEY `uuid` (`uuid`),
    KEY `is_dead` (`is_dead`),
    KEY `updated_at` (`updated_at`),
    KEY `followed_by` (`followed_by`),
    KEY `social_id` (`social_id`),
    KEY `is_private` (`is_private`),
    KEY `country_id` (`country_id`),
    FULLTEXT KEY `text_search` (`text_search`)) ENGINE = InnoDB AUTO_INCREMENT = 2278376 DEFAULT CHARSET = utf8

影响者

CREATE TABLE `locations` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `country_name` varchar(255) DEFAULT NULL,
    `city_name` varchar(255) DEFAULT NULL,
    `type` varchar(255) DEFAULT NULL,
    PRIMARY KEY (`id`),
    UNIQUE KEY `unique_index` (`city_name`, `country_name`),
    KEY `type` (`type`)
    USING BTREE) ENGINE = InnoDB AUTO_INCREMENT = 6479 DEFAULT CHARSET = utf8mb4

CREATE TABLE `influencers` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `bio` varchar(255) CHARACTER
    SET utf8mb4 DEFAULT NULL,
    `url` varchar(255) CHARACTER
    SET utf8mb4 DEFAULT NULL,
    `followed_by` int(11) DEFAULT NULL,
    `follows` int(11) DEFAULT NULL,
    `full_name` varchar(255) CHARACTER
    SET utf8mb4 NOT NULL,
    `social_id` varchar(255) DEFAULT NULL,
    `is_private` tinyint (1) DEFAULT NULL,
    `avatar` varchar(255) NOT NULL,
    `username` varchar(30) NOT NULL,
    `text_search` text CHARACTER
    SET utf8mb4 NOT NULL,
    `updated_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
    `uuid` varchar(255) DEFAULT NULL,
    `is_dead` tinyint (4) DEFAULT NULL,
    `country_id` int(11) DEFAULT NULL,
    `city_id` int(11) DEFAULT NULL,
    PRIMARY KEY (`id`),
    UNIQUE KEY `username` (`username`),
    UNIQUE KEY `uuid` (`uuid`),
    KEY `is_dead` (`is_dead`),
    KEY `updated_at` (`updated_at`),
    KEY `followed_by` (`followed_by`),
    KEY `social_id` (`social_id`),
    KEY `is_private` (`is_private`),
    KEY `country_id` (`country_id`),
    FULLTEXT KEY `text_search` (`text_search`)) ENGINE = InnoDB AUTO_INCREMENT = 2278376 DEFAULT CHARSET = utf8

可以使用内部联接来避免in子句

    SELECT
        `influencers`.*,
        `locations`.`country_name`
    FROM
        `influencers`
    INNER JOIN  (
        SELECT
                `influencer_uuid` FROM `category_influencer`
            WHERE
                `category_id` = 17
                AND `is_main` = 1

    ) T ON T.influencer_uuid = influencers.uuid
        LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id`
    WHERE
        `is_dead` = 0
        AND `is_private` = 0
        AND `country_id` = '31'

    ORDER BY
        `followed_by` DESC
    LIMIT 7 OFFSET 6

通过这种方式，您可以使用基于join的单个关系匹配，而不是对所有IN结果进行迭代，您可以使用内部join避免IN子句

    SELECT
        `influencers`.*,
        `locations`.`country_name`
    FROM
        `influencers`
    INNER JOIN  (
        SELECT
                `influencer_uuid` FROM `category_influencer`
            WHERE
                `category_id` = 17
                AND `is_main` = 1

    ) T ON T.influencer_uuid = influencers.uuid
        LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id`
    WHERE
        `is_dead` = 0
        AND `is_private` = 0
        AND `country_id` = '31'

    ORDER BY
        `followed_by` DESC
    LIMIT 7 OFFSET 6

通过这种方式，您可以使用基于连接的单个关系匹配，而不是对所有结果进行迭代，除非我遗漏了什么，否则您可以使用连接替换子选择：

SELECT influencers.*,
       locations.country_name
FROM influencers
         JOIN category_influencer T ON (
            T.influencer_uuid = influencers.uuid
            AND category_id = 17
            AND is_main = 1)
         LEFT JOIN locations ON influencers.country_id = locations.id
WHERE is_dead = 0
  AND is_private = 0
  AND country_id = '31'

ORDER BY followed_by DESC
LIMIT 7 OFFSET 6

除非我遗漏了什么，否则您可以将subselect替换为JOIN：

SELECT influencers.*,
       locations.country_name
FROM influencers
         JOIN category_influencer T ON (
            T.influencer_uuid = influencers.uuid
            AND category_id = 17
            AND is_main = 1)
         LEFT JOIN locations ON influencers.country_id = locations.id
WHERE is_dead = 0
  AND is_private = 0
  AND country_id = '31'

ORDER BY followed_by DESC
LIMIT 7 OFFSET 6

在每列前面加上它所属的表（或者更好，加上表的别名）。您可能很清楚每列的位置，但我们不清楚。另外，请向我们展示索引的代码。除了解释之外，有关查询性能的问题始终需要所有相关的show CREATE TABLE语句tables@TheImpaler我已经在上面的列前面加了前缀，在每个列前面加了表（或者更好，使用表的别名）它所属的位置。您可能很清楚每一列的位置，但我们不清楚。另外，请向我们展示索引的代码。除了解释之外，有关查询性能的问题始终需要所有相关的show CREATE TABLE语句tables@TheImpaler我已经预先准备了上面的专栏，谢谢，但这仍然需要13秒来执行，bu如果我删除对

category\u influencer

的查询，只需要不到1秒的时间。最奇怪的是，在每个被查询的

category\u influencer

列上都有索引-真的不知道如何优化它吗？谢谢，但这仍然需要13秒的时间来执行，但如果我删除对

ca的查询，只需要不到1秒的时间tegory_influencer

。最奇怪的是，在每个被查询的

类别_influencer

列上都有索引-真的不知道如何优化它吗？