《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

SELECT
    sum(staff_id = 1),
    sum(staff_id = 2)
FROM
    payment t;

2、创建表userinfo的语句

CREATE TABLE userinfo(
    id int unsigned not null auto_increment,
    name varchar(64) not null default '',
    email varchar(64) not null default '',
    password  varchar(64) not null default '',
    dob date default null,
    address  varchar(255) not null default '',
    city  varchar(64) not null default '',
    state_id tinyint unsigned not null default '0',
    zip  varchar(8) not null default '',
    country_id smallint unsigned not null default '0',
    gender enum('M','F') not null default 'M',
    account_type  varchar(32) not null default '',
    verified tinyint not null default '0',
    allow_mail tinyint unsigned not null default '0',
    parrent_account int unsigned not null default '0',
    closest_airport varchar(3) not null default '',
    primary key(id),
    unique key email(email),
    key country_id(country_id),
    key state_id(state_id),
    key state_id_2(state_id,city,address)
)ENGINE=innodb;

 3、通过STRAIGHT_JOIN干扰表的关联顺序

-- 通过STRAIGHT_JOIN干扰表的关联顺序/
EXPLAIN SELECT STRAIGHT_JOIN
    film.film_id,
    film.title,
    film.release_year,
    actor.actor_id,
    actor.first_name,
    actor.last_name
FROM
    sakila.film
INNER JOIN sakila.film_actor USING (film_id)
INNER JOIN sakila.actor USING (actor_id);

4、如何查看变量的值

show variables like  'optimizer_search_depth';