其他
自增主键,很多人以为自己懂了,然而...
drop table t1;
create table t1(
id int not null auto_increment,
name varchar(10) unique,
count int default 0,
primary key(id),
index(name)
)engine=innodb;
insert into t1(name) values("zhangsan"),("lisi"),("wangwu");
select * from t1;
画外音:初始值,是0还是1?
drop table t1,t2;
create table t1(
id int not null auto_increment,
name varchar(10) unique,
count int default 0,
primary key(id),
index(name)
)engine=innodb;
create table t2(
name varchar(10) unique
)engine=innodb;
insert into t2(name) values("x"),("y"),("z");
insert into t1(name) select name from t2;
select * from t1;
create table t1(
id int not null auto_increment,
name varchar(10) unique,
count int default 0,
primary key(id),
index(name)
)engine=innodb;
insert into t1(id, name) values(1, "shenjian");
insert into t1(id, name) values (111, "111"),(NULL, "abc"),(222, "222"),(NULL,"xyz");
select * from t1;
insert into t1(name)values("shenjian"),("aaa"),("bbb")
on duplicate key update count=100;
select * from t1;
(1)行锁还是表锁?
(2)事务范围加锁还是SQl语句范围加锁?
相关文章:
四个测验,你的答案是什么?