Advanced Mysql Exercises (1)

1. Modify book information

1. Create a book table

• Information stored in the book table (book number, book name, book category, book price)
  Note : Before creating the table, remember to delete the table habitually, in case there is a table before, and an error is reported!

drop table if exists books;
create table books(id int,
	name varchar(20),
	type varchar(20),
	price decimal(5,2)
);

2. Add data

insert into books values(1,'Java核心技术','计算机类',50.0),
	(2,'Mysql原理','计算机类',45.5),
	(2,'高等数学','必修类',20.5),
	(3,'计算机基础','计算机类',30.0);

3. Query the data in the table

select * from books;

4. Modify operations

• Modify the book information of "Java Core Technology" and modify the price to 61

update books set price = 61 where name like 'Java核心技术';
select * from books;

5. Delete operation

 delete from books where type = '计算机类';
 select * from books;

2. Commodity table operation

• Product table storage information (product number, product price, product inventory quantity)

1. Create a table

 drop table if exists goods;
create table goods(id int,
     price decimal(5,2),
     number int
     );

2. Increase the data in the table

insert into goods values(1,30.00,100),
	(2,35.5,200),
	(3,150,50);
select * from goods;

3. Alias ​​display data

select id 编号,price 价格, number 库存 from goods;

4. Modify the records of all commodities with inventory greater than 30, and increase the price by 50 yuan

update goods set price = price+50 where number > 30;
select * from goods; 

5. Delete records in the commodity table where the price is greater than 50 and less than 100

delete from goods where price > 50 and price < 100;
select id 编号,price 价格, number 库存 from goods;