SQL语句

单表数据一

create database test9;

1.在test9中创建一张表 user （整形id、字符串（50）username、字符串（32）password）

use test9;
create table `user`(
  id int primary key auto_increment ,       #主键 + 自动增长
  username varchar(50),
  `password` varchar(32)
);

2.向user表中插入3条数据

insert into `user`(username,`password`) values('jack','111');
insert into `user`(username,`password`) values('rose','222');
insert into `user`(username,`password`) values('tom','333');

3.查询user表中的所有数据

select * from `user`;

4.更新user表的第二条数据的密码为666666

update `user` set `password` = '666666' where id = 2;

5.删除user表的第一条数据

delete from `user` where id = 1;

6.计算user表中的总条数

select count(*) from `user`;

单表数据二

create table product(
    pid int primary key,
    pname varchar(20),
    price double,
    category_id varchar(32)
);

INSERT INTO product(pid,pname,price,category_id) VALUES(1,'联想',5000,'c001');
INSERT INTO product(pid,pname,price,category_id) VALUES(2,'海尔',3000,'c001');
INSERT INTO product(pid,pname,price,category_id) VALUES(3,'雷神',5000,'c001');

INSERT INTO product(pid,pname,price,category_id) VALUES(4,'JACK JONES',800,'c002');
INSERT INTO product(pid,pname,price,category_id) VALUES(5,'真维斯',200,'c002');
INSERT INTO product(pid,pname,price,category_id) VALUES(6,'花花公子',440,'c002');
INSERT INTO product(pid,pname,price,category_id) VALUES(7,'劲霸',2000,'c002');

INSERT INTO product(pid,pname,price,category_id) VALUES(8,'香奈儿',800,'c003');
INSERT INTO product(pid,pname,price,category_id) VALUES(9,'相宜本草',200,'c003');
INSERT INTO product(pid,pname,price,category_id) VALUES(10,'面霸',5,'c003');

INSERT INTO product(pid,pname,price,category_id) VALUES(11,'好想你枣',56,'c004');
INSERT INTO product(pid,pname,price,category_id) VALUES(12,'香飘飘奶茶',1,'c005');

INSERT INTO product(pid,pname,price,category_id) VALUES(13,'果9',1,NULL);

查询所有商品

SELECT * FROM product ;

查询商品名和商品价格

SELECT pname,price FROM product;

别名查询,使用as 关键字

SELECT pname pn ,price pr FROM product;

去掉重复值

SELECT DISTINCT price FROM product 

查询结果是表达式(运算查询):将所有商品价格+10进行显示

SELECT pid,pname,price+10,category_id FROM product ;

查询商品名称为“花花公子”的商品所有信息：

SELECT * FROM product WHERE pname='花花公子'

查询价格为800商品

SELECT * FROM product WHERE price='800'

查询价格不是800的所有商品

SELECT * FROM product WHERE price !='800'

查询商品价格大于60元的所有商品信息

SELECT * FROM product WHERE price>60

查询商品价格在200到1000之间所有商品

SELECT * FROM product WHERE price>='200' AND price<='1000'

查询商品价格是200或800的所有商品

SELECT * FROM product WHERE price='200' OR price='800'

查询含有'霸'字的所有商品

SELECT * FROM product WHERE pname LIKE '%霸%'

查询以'香'开头的所有商品

SELECT * FROM product WHERE pname LIKE '%香%%'

查询第二个字为'想'的所有商品

SELECT * FROM product WHERE pname LIKE '%%想%'

商品没有分类的商品

SELECT * FROM product WHERE category_id IS NULL

查询有分类的商品

SELECT * FROM product WHERE category_id IS NOT NULL

1.链接查询.png