Walking into MySQL --- practice learning how to build tables, realize addition, modification and deletion

 Below I will share with you a simple exercise, which is very helpful for beginners, including how to create a table, add a primary key, insert data, and implement addition, deletion, modification, and query operations.

1. Create a table

1. Create a product table according to the requirements, the requirements are as follows.

Column definition Column name Data type Constraints

Commodity id                         product_id                           fixed-length string type ( 4 ) non-empty, primary key

Product name                     product_name                    variable length string type ( 100 ) non-empty

Product type                     product_type                       variable length string ( 4 ) non-empty

Sales price                     sale_price                                  Integer type

purchase price                     purchase_price                         integer type

Registration date                     regist_date                               date type

Table：product

CREATE TABLE Product
(produnct_id   CHAR(4)       NOT NULL PRIMARY KEY,
 product_name  VARCHAR(100)  NOT NULL,
 product_type  VARCHAR(32)   NOT NULL,
 sale_price     INTEGER ,
 purchase_price INTEGER ,
 regist_date    DATE);

  2. Insert data

1. Insert the following data into the product table

            '0001', 'T-shirt' ,'clothes', 1000, 500, '2009-09-20'

            '0002', 'Hole Punch', 'Office Supplies', 500, 320, '2009-09-11'

            '0003', 'Sports T-shirt', 'Clothes', 4000, 2800, NULL

            '0004', 'Chopper', 'Kitchen Utensils', 3000, 2800, '2009-09-20'

            '0005', 'Pressure Cooker', 'Kitchen Appliance', 6800, 5000, '2009-01-15'

            '0006', 'fork', 'kitchenware', 500, NULL, '2009-09-20'

            '0007', 'grater', 'kitchen utensils', 880, 790, '2008-04-28'

            '0008', 'Ballpoint Pen', 'Office Supplies', 100, NULL, '2009-11-11'

INSERT INTO Product VALUES('0001', 'T恤' ,'衣服', 1000, 500, '2009-09-20');
INSERT INTO Product VALUES('0002', '打孔器', '办公用品', 500, 320, '2009-09-11');
INSERT INTO Product VALUES('0003', '运动T恤', '衣服', 4000, 2800, NULL);
INSERT INTO Product VALUES('0004', '菜刀', '厨房用具', 3000, 2800, '2009-09-20');
INSERT INTO Product VALUES('0005', '高压锅', '厨房用具', 6800, 5000, '2009-01-15');
INSERT INTO product VALUES('0006', '叉子', '厨房用具', 500, NULL, '2009-09-20');
INSERT INTO product VALUES('0007', '擦菜板', '厨房用具', 880, 790, '2008-04-28');
INSERT INTO Product VALUES('0008', '圆珠笔', '办公用品', 100, NULL, '2009-11-11');

  

3. Update data

1. Change product_name hole punch to stapler

UPDATE <表名> SET <列名=更新值> WHERE <更新条件>

UPDATE product SET product_name='订书机' WHERE product_name='打孔器';

     2. Increase the price of sale_price less than or equal to 500 yuan by 50 

UPDATE product SET sale_price=sale_price+50 WHERE sale_price<=500;

 

 

Fourth, view the data 

1. Write a SQL statement to select the products whose registration date (regist_date) is after April 28, 2009 from the Product table. The query result should contain two columns product_name and regist_date.

SELECT <列名>
FROM   <表名>
WHERE  <查询条件表达式>
ORDER BY <排序的列名> ASC或者DESC

SELECT product_name,regist_date FROM product WHERE regist_date>'2009-4-28';

 

2. Please write a SELECT statement to select records from the Product table that meet the condition of "office supplies and kitchen utensils whose profit is higher than 100 yuan after a 10% discount on the sales unit price". The query result should include the product_name column, product_type column, and the profit after the 10% discount on the sales unit price (the alias is set to profit)

SELECT product_name,product_type,sale_price*0.9-purchase_price profit FROM product WHERE (product_type='办公用品' OR  product_type='厨房用具') 
AND sale_price*0.9-purchase_price>100;

              

 3. Filter out the product_name, sale_price, purchase_price of products whose sale_price is 500 yuan or more higher than purchase_price.

SELECT product_name,sale_price,purchase_price FROM product WHERE sale_price-purchase_price>=500;

   

 4. Print out the information of all products whose sales price is between 1000 and 4000

SELECT * FROM product WHERE sale_price BETWEEN 1000 AND 4000;

 5. Find all the products whose sales price is greater than or equal to 4000 and arrange them in descending order of purchase price

SELECT * FROM product WHERE sale_price>=4000 ORDER BY purchase_price DESC;

 5. Delete data

  1. Delete the library and run away

DELETE FROM <表名>; 删库跑路

  2. Delete data - try it yourself! !

DELETE FROM 表名 WHERE <限制条件>

例如：DELETE FROM product WHERE product_id='0005';