主键,聚集索引,不是一个东西!
(1) create table user(
name varchar(10)
)engine=innodb;
(2) insert into user values('shenjian');
(3) insert into user values('shenjian');
A 建表语句(1)报错
B 插入语句(2)报错
C 插入语句(3)报错
D 均不报错
(1) create table user(
id int,
name varchar(10),
primary key(id)
)engine=innodb;
(2) insert into user(name) values('shenjian');
(3) insert into user(name) values('shenjian');
A 建表语句(1)报错
B 插入语句(2)报错
C 插入语句(3)报错
D 均不报错
画外音:这一题很多人答错。
(1) create table user(
id int not null,
name varchar(10) not null,
primary key(id, name)
)engine=innodb;
(2) insert into user values(1, 'shenjian');
(3) insert into user values(1, 'zhangsan');
(4) insert into user values(2, 'shenjian');
A 建表语句(1)报错
B 插入语句(2)报错
C 插入语句(3)报错
D 插入语句(3)报错
E 均不报错
(1) create table user(
id int auto_increment,
name varchar(10) not null,
primary key(id)
)engine=innodb;
(2) insert into user(name) values('shenjian');
(3) insert into user(id, name) values(10,'shenjian');
(4) insert into user(name) values('shenjian');
A 建表语句(1)报错
B 插入语句(2)报错
C 插入语句(3)报错
D 插入语句(3)报错
E 均不报错
(1) create table user(
id int auto_increment,
name varchar(10) not null,
primary key(name, id)
)engine=innodb;
(2) insert into user(name) values('shenjian');
(3) insert into user(id, name) values(10,'shenjian');
(4) insert into user(name) values('shenjian');
A 建表语句(1)报错
B 插入语句(2)报错
C 插入语句(3)报错
D 插入语句(3)报错
E 均不报错
画外音:这一题很多人答错。
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【DCEEA】,你答对了吗?
画外音:原文是《主键,五个小习题》,评论里好多同学都答错了,帮转一下吧。