MySQL数据库之索引

create table test1(
      id int primary key AUTO_increment,
      name varchar (20),
      salary int default  1000
);
insert into test1 (name)values ('111'),("222"),("333"),("444");

select *from test1 where id=3;

--唯一索引unique  唯一索引不可重复

alter table test1 modify name varchar (20) unique;

--创建索引格式
create table A(
    id int primary key,
    name varchar (20),
    unique|fulltext|spatial    index|key   [索引名] (字段名(长度)) [ASC|DESC]
);
--创建索引

create table stu(
      id int,
      name varchar (20),
      index index_name (name)
      );

--唯一索引（字段不能重复name）

create table stu1(
      id int,
      name varchar (20),
      unique index index_name (name)
      );

--全文索引

create table stu2(
  id int,
  name varchar (10),
  resume varchar (20),
  fulltext index index_resume (resume)
);

--创建多条索引

create table stu3(
  id int,
  name varchar (10),
  resume varchar (20),
  index index_resume (name,resume)
);

create table t1(id int,name varchar (20));

--修改结束符
delimiter $$
create procedure autoinsert()
begin
declare i int default 1;
while(i<50)do
insert into t1 values (i,"alex");
set i=i+1;
end while;
end$$

delimiter ;
call autoinsert();

-- 添加索引

-- create在已存在表上创建索引
create [unique|fulltext|apatial] index index_name on table_name (字段名[(长度)]) [ASC|DESC];
--alter table 在已存在表上创建索引
alter table table_name add [unique|fulltext|apatial] index index_name (字段名[(长度)]) [ASC|DESC];

--删除索引：

drop index index_name on st1;