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  • 《高性能MySQL》语句片段

    chapter05  创建高性能的索引

    1、这样的语句是可以存在的

    1 SELECT
    2     sum(staff_id = 1),
    3     sum(staff_id = 2)
    4 FROM
    5     payment t;
    View Code

    2、创建表userinfo的语句

     1 CREATE TABLE userinfo(
     2     id int unsigned not null auto_increment,
     3     name varchar(64) not null default '',
     4     email varchar(64) not null default '',
     5     password  varchar(64) not null default '',
     6     dob date default null,
     7     address  varchar(255) not null default '',
     8     city  varchar(64) not null default '',
     9     state_id tinyint unsigned not null default '0',
    10     zip  varchar(8) not null default '',
    11     country_id smallint unsigned not null default '0',
    12     gender enum('M','F') not null default 'M',
    13     account_type  varchar(32) not null default '',
    14     verified tinyint not null default '0',
    15     allow_mail tinyint unsigned not null default '0',
    16     parrent_account int unsigned not null default '0',
    17     closest_airport varchar(3) not null default '',
    18     primary key(id),
    19     unique key email(email),
    20     key country_id(country_id),
    21     key state_id(state_id),
    22     key state_id_2(state_id,city,address)
    23 )ENGINE=innodb;
    View Code

     3、通过STRAIGHT_JOIN干扰表的关联顺序

     1 -- 通过STRAIGHT_JOIN干扰表的关联顺序/
     2 EXPLAIN SELECT STRAIGHT_JOIN
     3     film.film_id,
     4     film.title,
     5     film.release_year,
     6     actor.actor_id,
     7     actor.first_name,
     8     actor.last_name
     9 FROM
    10     sakila.film
    11 INNER JOIN sakila.film_actor USING (film_id)
    12 INNER JOIN sakila.actor USING (actor_id);
    View Code

    4、如何查看变量的值

    1 show variables like  'optimizer_search_depth';
    View Code
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  • 原文地址:https://www.cnblogs.com/mryanglin/p/6741103.html
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