一文带你了解MySQL中的锁机制

create database test_lock;
use test_lock;
 
drop table tb_book ;
 
create table tb_book(
	id int(11) auto_increment,
	name varchar(50) default null,
	publish_time date default null,
	status char(1) default null,
	primary key (id)
)engine=myisam default charset=utf8;
 
insert into tb_book values(null,'sql','2088-08-01','1');
insert into tb_book values(null,'sql',20880908,'0');
 
 
create table tb_user(
	id int(11) auto_increment,
	name varchar(50) default null,
	primary key (id)
	
)engine =myisam default charset=utf8;
 
insert into tb_user values(null,'张三');
insert into tb_user values(null,'李四');
 
-- 加读锁
lock table tb_book read;
 
select * from tb_book  ;-- 能正常输出
select * from tb_book tb ;-- 不能正常输出，不能有别名
update tb_book set status=1;-- 不能正常输出 读锁：可读不可改
 
select * from tb_user ;-- 不能正常输出,当锁住一个表时也不能看其他表
-- 解锁
unlock tables;

create table tb_book(
	id int(11) auto_increment,
	name varchar(50) default null,
	publish_time date default null,
	status char(1) default null,
	primary key (id)
)engine=myisam default charset=utf8;
 
insert into tb_book values(null,'sql','2088-08-01','1');
insert into tb_book values(null,'sql',20880908,'0');
 
 
create table tb_user(
	id int(11) auto_increment,
	name varchar(50) default null,
	primary key (id)
	
)engine =myisam default charset=utf8;
 
insert into tb_user values(null,'张三');
insert into tb_user values(null,'李四');
 
-- 加写锁
lock table tb_book write;
 
select * from tb_book  ;-- 能正常输出
select * from tb_book tb ;-- 不能正常输出，不能有别名
update tb_book set status=1;-- 可以修改 写锁：可读可修改，但在没有解锁之前不能被其他人查看，会被挂起
 
select * from tb_user ;-- 不能正常输出,当锁住一个表时也不能看其他表
-- 解锁
unlock tables;

-- 行锁
 
drop table is exists test_innodb_lock;
create table test_innodb_lock(
	id int(11),
	name varchar(16),
	sex varchar(1)
)engine=innodb;
 
insert into test_innodb_lock values(1,'100','1'),
									(2,'200','0'),
									(3,'200','1'),
									(4,'300','0'),
									(5,'400','0'),
									(6,'500','1'),
									(7,'600','1'),
									(1,'700','1');
 
create index index_id on test_innodb_lock(id);
create index index_name on test_innodb_lock(name);