Mariadb
Date: . Last updated: .
SQL
常用命令
systemctl start mariadb;
systemctl status mariadb;
systemctl stop mariadb;
systemctl restart mariadb;
mysqladmin -u root -p password '123456';
mariadb -u root -p'raymond'
show databases;
use sql_hr; //使用库
show tables;// employe offices
show create table offices;
drop databases ; // 删库
create database dbtest1; // 建库
show create table dbtest1;
create table emplyees(id int, name varchar(15)); //建表
DROP TABLE table_name ;// 删表
insert into emplyees values(1001, "TOM"); // 往表添加数据
CREATE DATABASE Database_name;
USE database_name;
DROP DATABASE Database_name;
DROP TABLE table_name ;
DDL：数据定义语言 CREATE / ALTER / DROP / RENAME / TRUNCATE
DML: 数据操作语言 INSERT / DELETE / UPDATE / SELECT
DCL: 数据控制语言 COMMIT / ROLLBACK / SAVEPOINT / GRANT / REVOKE
SELECT department_id, MAX(salary)
FROM employee
WHERE department_id IN (10, 20, 30, 40) -- 过滤条件中没有聚合函数时，建议声明在WHERE子句中
GROUP BY department_id
HAVING MAX(salary) > 1000 -- 过滤条件中有聚合函数时, 过滤条件必须声明在HAVING子句中
-- 2
SELECT ...............(存在聚合函数)
-- 1
FROM .......（LEFT / RIGHT)JOIN....... ON ........ 多表连接
WHERE
GROUP BY ......
HAVING .......包含聚合函数的过滤条件
-- 3
ORDER BY ..........(ASC/ DESC)
LIMIT ........... 分页
单行子查询/多行子查询
INSERT INTO employee(id, name, salary)
VALUES
(1, 'jack', 8000)
(3, 'tom', 9000)
UPDATE employee(id, name, salary) -- 更新/删除可能因为约束失败
SET salary = 1200
WHERE id = 1