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Mysql database -dql

2022-07-03 16:40:00 【Don't go to graduate school, don't change your name TL】

Single table query

Data preparation

--  establish db1 database 
CREATE DATABASE db1;

--  Use db1 database 
USE db1;

--  Create data table 
CREATE TABLE product(
	id INT,				--  Product id 
	NAME VARCHAR(20),	--  Name of commodity 
	price DOUBLE,		--  commodity price 
	brand VARCHAR(10),	--  Brand of goods 
	stock INT,			--  inventory 
	insert_time DATE    --  Add the time 
);

--  Add data 
INSERT INTO product VALUES (1,' Huawei mobile phones ',3999,' Huawei ',23,'2088-03-10'),
(2,' Mi phones ',2999,' millet ',30,'2088-05-15'),
(3,' Apple mobile phone ',5999,' Apple ',18,'2088-08-20'),
(4,' Huawei's computer ',6999,' Huawei ',14,'2088-06-16'),
(5,' Xiaomi computer ',4999,' millet ',26,'2088-07-08'),
(6,' Apple computer ',8999,' Apple ',15,'2088-10-25'),
(7,' Lenovo computer ',7999,' lenovo ',NULL,'2088-11-11');

Created a db1 The database of , It contains product The table is shown below ：

The query syntax

select
   Field list
from
   List of table names
where
   List of conditions
group by
   Grouping field
having
   Grouping after Conditions （ Cannot use after grouping where, Only use having）
order by
   Sort
limit
   Paging limit