数据库|mysql教程
values,price
数据库-mysql教程
1.插入数据
insert into表名(列名1,列名2,列名..) values(值1,值2,值…); insert into product(name, price, pic_path) values(‘Nike’,500,’uploads/3245.jpg’);
2.更新数据
update 表名set列名1=值1,列名2=值2[where条件]; update product set name=’LiNing’, price=50where id=2;
3.删除数据
deletefrom表名[where条件]; deletefrom product where id=2;
4.查询所有数据
select*from表名;select*from product;
5.查询部份列
select列名1,列名2,列名N from表名;select name, price from product;
6.条件查询
# 比较 =, , =, !=select*from表名where列名=值;select*from product where id=2;# and 与 select*from表名where条件1and条件2and条件N; select*from product where name=’Nike’and price=50;# or 或 select*from表名where条件1or条件2or条件N;select*from product where name=’Nike’or price>50; # not 非 select*from表名wherenot条件1;select*from product wherenot name=’Nike’; #in 枚举 select*from表名where列名in(值1,值2,值N); select*from product where id in(2,3,4,10); select*from product where id notin(2,3,4,10); #like 模糊查询 select*from表名where列名 like ‘%值%’; select*from product where name like ‘%Li%’; #between…and… 范围查询 select*from表名where列名 between 值and值; select*from order where created between ‘-01-01’and’-01-01’;
7.查询排序
select*from表名 order by列名排序方式;#排序方式: asc(升序，默认)，desc(降序) select*from product order by created desc;
8.限制查询结果数量
select*from表名 limit 开始记录数,结果数量;select*from product limit 5;select*from product limit 2,5;
9.聚合函数
# count 总记录数 select count(列名)from student; select count(id)from student; # sum 总共 select sum(列名)from student; select sum(age)from student; # avg 平均值 select avg(列名)from student;select avg(age)as avg_age from student; # max 最大值 select max(列名)from student; select max(age)from student; # min 最小值 select min(列名)from student; select min(age)from student;
10.子查询
select name from student where age<(select avg(age)from student ); select*from product where id in(select id from order );
11.连接查询
select s.username as stu_name, t.name as te_name from student s, teacher t where s.teacher_id=t.id;
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