1.插入:insert
创建一个表
create table student {
id int primary key auto_increment,
sno int not null unique ,
name varchar(20) not null,
tel varchar(20)
}
1. 全列插入
insert into student values(1,1001,"张三",123345678);
2. 指定列插入
insert into student (id,sno,name) values(1,1001,"张三");
3. 指定列插入冲突时进行修改
方法一:
insert into … values(… ) on duplicate key update …
insert into student (id,sno,name) values(1,1001,"张三") on duplicate key update sno=1001 name="张三"
**方法二:**先删除,在插入
replace into tablename ( …) values(… )
replace into student (id,sno,name) values(1,1001,"张三");"
2.检索:select
1. 查询所有
select * from student;
2. 指定列查询
select id,name from student ;
3.查询结果去重:distinct
select distinct id ,name from student ;
4.查询结果指定别名:as(可以省略)
select column [as] alias_name […] from tablename
select id,sno,name sname from student;
3.条件:where
1. 运算符
2.运算符
create table exam(
id int unsigned primary key AUTO_INCREMENT,
name varchar(20) NOT NULL COMMENT '同学姓名',
chinese float default 0.0 COMMENT '语⽂成绩',
math float default 0.0 COMMENT '数学成绩',
english float default 0.0 COMMENT '英语成绩'
);
1. 基本比较
//英语不及格的同学及英语成绩 ( >80 )
select name ,chinses from exam chinses>80;
2. 使用 AND 进行条件连接
//语⽂成绩在 [80, 90] 分的同学及语⽂成绩
select id,name from student ;
3.查询结果去重:distinct
select distinct id ,name from student ;
4.查询结果指定别名:as(可以省略)
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