Summary of commonly used basic SQL statements in MySQL_MySQL

1. Common commands

Connect local database and remote database (172.16.xx.xx:3306):

mysql -h localhost -u root -p123 
mysql -h 172.16.xx.xx -P 3306 -u root -p 

2. DDL

Data Definition Language (DDL) defines the database schema, including CREATE, ALTER, DROP, TRUNCATE, COMMENT and RENAME statements.

CREATE

The create statement creates a table:

CREATE TABLE `device_label` (
`id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键-自增长ID',
`origin_model` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '收集机型',
`origin_vendor` varchar(64) COLLATE utf8_bin NOT NULL COMMENT '收集厂商',
`vendor` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '标注厂商',
`model` varchar(32) COLLATE utf8_bin NOT NULL COMMENT '标注品牌',
PRIMARY KEY (`id`),
UNIQUE KEY `device_key` (`origin_model`,`origin_vendor`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='设备标注表'; 
改（ALTER）

ALTER TABLE changes the structure of the table and supports the following operations,

Modify column type and column name:

alter table device_label modify origin_model varchar(32);
alter table device_label change origin_model device_model varchar(16); 

Append column:

alter table device_label add os_type varchar(8) COLLATE utf8_bin NOT NULL COMMENT '操作系统' after id; 

Modify the order between columns:

alter table device_label modify os_type varchar(8) after origin_model; 

Modify primary key:

alter table device_label drop primary key, add primary key (`origin_model`,`origin_vendor`); 

TRUNCATE

TRUNCATE clears the table, which is equivalent to delete from without specifying the where condition.

truncate device_label;

3. DCL

Data Control Language (DCL) is used for user permission management, including GRANT and REVOKE commands.

GRANT

MySQL has very fine permission control:

•Detailed permission classification
•DB -> Table -> Column, granularity of permissions
•Control the host (wildcard matching available)

Create a hive user and grant localhost permission to access all tables in db1:

CREATE USER 'hive'@'localhost' IDENTIFIED BY 'mypass';
GRANT ALL ON db1.* TO 'hive'@'localhost';
-- 可简写为
GRANT ALL ON db1.* TO 'hive'@'localhost' IDENTIFIED BY 'mypass'; 

You can also only grant select permission to a certain table:

GRANT SELECT ON db2.invoice TO 'hive'@'localhost'; 

4. DML

Data manipulation language (DML) is mainly used to express database queries and updates, including additions, deletions, modifications (INSERT, UPDATE, DELETE, SELECT).

INSERT

Add row data:

insert into device_label (origin_model, origin_vendor, vendor, model)
values (
'h9', 'bbk', '步步高', 'H9'
); 

Copy one table to another table:

insert into device_label_copy (`origin_model`, `origin_vendor`, `vendor`, `model`)
select `origin_model`, `origin_vendor`, `vendor`, `model`
from device_label; 

In addition, MySQL supports loading structured plain text into the database via load data:

load data local infile 'dvc-label.csv'
into table device_label
fields terminated by ','
ignore 1 lines
(origin_model, origin_vendor, vendor, model); 

If ERROR 1148 (42000) error occurs, use the mysql --local-infile -u user -ppasswd command to enter mysql.

Update

Update column value:

update device_label 
set origin_model = 't2', origin_vendor = 'xiami'
where vendor = '锤子'; 

DELETE

Delete rows based on where condition:

delete from device_label where origin_vendor = 'alps'; 

Check (SELECT)

Query manufacturers with more than 10 marked models:

select vendor, count(distinct model) as models
from device_label
group by vendor
having models > 10

The above is a summary of the commonly used basic SQL statements in MySQL introduced by the editor. I hope it will be helpful to you. If you have any questions, please leave me a message and the editor will reply to you in time. Thank you very much for your support of the website!