个人主页：Guiat
归属专栏：MySQL
文章目录
- 1. MySQL基础命令
- 1.1 连接MySQL
- 1.2 基本命令概览
- 2. 数据库操作
- 2.1 创建数据库
- 2.2 查看数据库
- 2.3 选择数据库
- 2.4 修改数据库
- 2.5 删除数据库
- 2.6 数据库备份与恢复
- 3. 表操作基础
- 3.1 创建表
- 3.2 查看表信息
- 3.3 创建临时表
- 3.4 创建表的复制
- 4. 表结构修改
- 4.1 添加列
- 4.2 修改列
- 4.3 删除列
- 4.4 重命名表
- 4.5 删除表
- 5. 约束与键
- 5.1 主键约束
- 5.2 外键约束
- 5.3 唯一约束
- 5.4 检查约束
- 5.5 默认值约束
- 6. 索引操作
- 6.1 创建索引
- 6.2 查看索引
- 6.3 删除索引
- 7. 表数据操作
- 7.1 插入数据
- 7.2 更新数据
- 7.3 删除数据
- 7.4 查询数据
- 8. 高级表操作
- 8.1 表分区
- 8.2 视图操作
- 8.3 存储过程
- 9. 事务控制
- 9.1 事务基本操作
- 9.2 设置保存点
- 9.3 事务隔离级别
- 10. 实际应用案例
- 10.1 电子商务数据库设计
- 10.2 数据库维护操作
- 10.3 常见查询和操作示例
正文
1. MySQL基础命令
MySQL是一种流行的关系型数据库管理系统，掌握基本的数据库和表操作命令是使用MySQL的基础。
1.1 连接MySQL
# 连接本地MySQL服务器
mysql -u username -p
# 连接远程MySQL服务器
mysql -h hostname -u username -p -P port
1.2 基本命令概览
-- 显示MySQL版本
SELECT VERSION();
-- 显示当前日期时间
SELECT NOW();
-- 显示当前用户
SELECT USER();
-- 显示可用的命令
HELP;
-- 退出MySQL客户端
EXIT;
-- 或
QUIT;
2. 数据库操作
2.1 创建数据库
-- 基本语法
CREATE DATABASE database_name;
-- 指定字符集和排序规则
CREATE DATABASE database_name
CHARACTER SET utf8mb4
COLLATE utf8mb4_unicode_ci;
-- 仅当数据库不存在时创建
CREATE DATABASE IF NOT EXISTS database_name;
2.2 查看数据库
-- 显示所有数据库
SHOW DATABASES;
-- 显示创建数据库的SQL语句
SHOW CREATE DATABASE database_name;
-- 显示数据库状态
SHOW STATUS;
2.3 选择数据库
-- 切换到指定数据库
USE database_name;
-- 查看当前选中的数据库
SELECT DATABASE();
2.4 修改数据库
-- 修改数据库字符集
ALTER DATABASE database_name
CHARACTER SET = utf8mb4;
-- 修改数据库排序规则
ALTER DATABASE database_name
COLLATE = utf8mb4_unicode_ci;
2.5 删除数据库
-- 删除数据库
DROP DATABASE database_name;
-- 仅当数据库存在时删除
DROP DATABASE IF EXISTS database_name;
2.6 数据库备份与恢复
# 使用mysqldump备份数据库
mysqldump -u username -p database_name > backup_file.sql
# 恢复数据库
mysql -u username -p database_name < backup_file.sql
3. 表操作基础
3.1 创建表
-- 基本表创建语法
CREATE TABLE table_name (
column1 datatype constraints,
column2 datatype constraints,
...
columnN datatype constraints
);
-- 示例：创建学生表
CREATE TABLE students (
student_id INT PRIMARY KEY AUTO_INCREMENT,
first_name VARCHAR(50) NOT NULL,
last_name VARCHAR(50) NOT NULL,
email VARCHAR(100) UNIQUE,
birth_date DATE,
enrollment_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
active BOOLEAN DEFAULT TRUE
);
3.2 查看表信息
-- 显示当前数据库的所有表
SHOW TABLES;
-- 显示表结构
DESCRIBE table_name;
-- 或
DESC table_name;
-- 显示创建表的SQL语句
SHOW CREATE TABLE table_name;
-- 显示表状态
SHOW TABLE STATUS LIKE 'table_name';
3.3 创建临时表
临时表在会话结束时自动删除：
-- 创建临时表
CREATE TEMPORARY TABLE temp_table (
id INT,
name VARCHAR(50)
);
3.4 创建表的复制
-- 复制表结构
CREATE TABLE new_table LIKE original_table;
-- 复制表结构和数据
CREATE TABLE new_table AS SELECT * FROM original_table;
-- 复制表结构和部分数据
CREATE TABLE new_table AS
SELECT * FROM original_table WHERE condition;
4. 表结构修改
4.1 添加列
-- 添加新列
ALTER TABLE table_name
ADD COLUMN column_name datatype constraints;
-- 在特定位置添加列
ALTER TABLE table_name
ADD COLUMN column_name datatype constraints
AFTER existing_column;
-- 添加列到表的第一个位置
ALTER TABLE table_name
ADD COLUMN column_name datatype constraints
FIRST;
-- 添加多列
ALTER TABLE table_name
ADD COLUMN column1 datatype constraints,
ADD COLUMN column2 datatype constraints;
4.2 修改列
-- 修改列的数据类型
ALTER TABLE table_name
MODIFY COLUMN column_name new_datatype;
-- 修改列名和数据类型
ALTER TABLE table_name
CHANGE COLUMN old_column_name new_column_name new_datatype constraints;
-- 修改列的默认值
ALTER TABLE table_name
ALTER COLUMN column_name SET DEFAULT default_value;
-- 删除列的默认值
ALTER TABLE table_name
ALTER COLUMN column_name DROP DEFAULT;
4.3 删除列
-- 删除单列
ALTER TABLE table_name
DROP COLUMN column_name;
-- 删除多列
ALTER TABLE table_name
DROP COLUMN column1,
DROP COLUMN column2;
4.4 重命名表
-- 重命名表
RENAME TABLE old_table_name TO new_table_name;
-- 或使用ALTER TABLE
ALTER TABLE old_table_name
RENAME TO new_table_name;
4.5 删除表
-- 删除表
DROP TABLE table_name;
-- 仅当表存在时删除
DROP TABLE IF EXISTS table_name;
-- 删除多个表
DROP TABLE table1, table2, table3;
5. 约束与键
5.1 主键约束
-- 创建表时定义主键
CREATE TABLE products (
product_id INT PRIMARY KEY,
product_name VARCHAR(100) NOT NULL
);
-- 复合主键
CREATE TABLE order_items (
order_id INT,
product_id INT,
quantity INT NOT NULL,
PRIMARY KEY (order_id, product_id)
);
-- 为已有的表添加主键
ALTER TABLE table_name
ADD PRIMARY KEY (column_name);
-- 删除主键
ALTER TABLE table_name
DROP PRIMARY KEY;
5.2 外键约束
-- 创建表时定义外键
CREATE TABLE orders (
order_id INT PRIMARY KEY,
customer_id INT,
order_date DATE,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
);
-- 为已有的表添加外键
ALTER TABLE orders
ADD CONSTRAINT fk_customer
FOREIGN KEY (customer_id) REFERENCES customers(customer_id);
-- 添加带有删除和更新行为的外键
ALTER TABLE orders
ADD CONSTRAINT fk_customer
FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
ON DELETE CASCADE
ON UPDATE CASCADE;
-- 删除外键约束
ALTER TABLE orders
DROP FOREIGN KEY fk_customer;
5.3 唯一约束
-- 创建表时定义唯一约束
CREATE TABLE users (
user_id INT PRIMARY KEY,
username VARCHAR(50) UNIQUE,
email VARCHAR(100) UNIQUE
);
-- 为已有的表添加唯一约束
ALTER TABLE users
ADD CONSTRAINT uq_email UNIQUE (email);
-- 删除唯一约束
ALTER TABLE users
DROP INDEX uq_email;
5.4 检查约束
MySQL 8.0及以上版本支持CHECK约束：
-- 创建表时定义检查约束
CREATE TABLE employees (
employee_id INT PRIMARY KEY,
name VARCHAR(100),
salary DECIMAL(10,2) CHECK (salary > 0),
age INT CHECK (age >= 18)
);
-- 为已有的表添加检查约束
ALTER TABLE employees
ADD CONSTRAINT chk_salary CHECK (salary > 0);
-- 删除检查约束
ALTER TABLE employees
DROP CHECK chk_salary;
5.5 默认值约束
-- 创建表时定义默认值
CREATE TABLE articles (
article_id INT PRIMARY KEY,
title VARCHAR(200) NOT NULL,
content TEXT,
published BOOLEAN DEFAULT FALSE,
created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
-- 为已有的列添加默认值
ALTER TABLE articles
ALTER COLUMN published SET DEFAULT TRUE;
-- 删除默认值
ALTER TABLE articles
ALTER COLUMN published DROP DEFAULT;
6. 索引操作
6.1 创建索引
-- 创建普通索引
CREATE INDEX idx_name ON table_name (column_name);
-- 创建唯一索引
CREATE UNIQUE INDEX idx_email ON users (email);
-- 创建复合索引
CREATE INDEX idx_name_email ON users (name, email);
-- 创建前缀索引
CREATE INDEX idx_title ON articles (title(50));
-- 在表创建时定义索引
CREATE TABLE customers (
id INT PRIMARY KEY,
name VARCHAR(100),
email VARCHAR(100),
INDEX idx_name (name)
);
-- 使用ALTER TABLE添加索引
ALTER TABLE customers
ADD INDEX idx_email (email);
6.2 查看索引
-- 查看表的所有索引
SHOW INDEX FROM table_name;
6.3 删除索引
-- 删除索引
DROP INDEX index_name ON table_name;
-- 使用ALTER TABLE删除索引
ALTER TABLE table_name
DROP INDEX index_name;
7. 表数据操作
7.1 插入数据
-- 插入单行数据
INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);
-- 插入多行数据
INSERT INTO table_name (column1, column2, ...)
VALUES
(value1, value2, ...),
(value1, value2, ...),
(value1, value2, ...);
-- 插入所有列的数据
INSERT INTO table_name
VALUES (value1, value2, ...);
-- 从另一个表插入数据
INSERT INTO target_table (column1, column2, ...)
SELECT column1, column2, ...
FROM source_table
WHERE condition;
7.2 更新数据
-- 更新所有行
UPDATE table_name
SET column1 = value1, column2 = value2
WHERE condition;
-- 使用子查询更新数据
UPDATE table_name
SET column1 = (SELECT column2 FROM another_table WHERE condition)
WHERE condition;
-- 多表更新
UPDATE table1 t1
JOIN table2 t2 ON t1.id = t2.id
SET t1.column1 = t2.column2
WHERE condition;
7.3 删除数据
-- 删除满足条件的行
DELETE FROM table_name
WHERE condition;
-- 删除所有行
DELETE FROM table_name;
-- 截断表（更快但不可回滚）
TRUNCATE TABLE table_name;
-- 多表删除
DELETE t1 FROM table1 t1
JOIN table2 t2 ON t1.id = t2.ref_id
WHERE condition;
7.4 查询数据
-- 基本查询
SELECT column1, column2
FROM table_name
WHERE condition;
-- 查询所有列
SELECT * FROM table_name;
-- 查询唯一值
SELECT DISTINCT column FROM table_name;
-- 使用条件查询
SELECT * FROM table_name
WHERE column = value AND/OR another_column > value;
-- 使用排序
SELECT * FROM table_name
ORDER BY column1 ASC, column2 DESC;
-- 使用限制
SELECT * FROM table_name
LIMIT 10 OFFSET 20;
-- 分组查询
SELECT column1, COUNT(*) as count
FROM table_name
GROUP BY column1
HAVING count > 5;
8. 高级表操作
8.1 表分区
-- 创建分区表（按范围分区）
CREATE TABLE sales (
id INT,
amount DECIMAL(10,2),
sale_date DATE
)
PARTITION BY RANGE (YEAR(sale_date)) (
PARTITION p0 VALUES LESS THAN (2020),
PARTITION p1 VALUES LESS THAN (2021),
PARTITION p2 VALUES LESS THAN (2022),
PARTITION p3 VALUES LESS THAN MAXVALUE
);
-- 查看分区信息
SHOW CREATE TABLE sales;
SELECT * FROM information_schema.PARTITIONS
WHERE TABLE_NAME = 'sales';
8.2 视图操作
-- 创建视图
CREATE VIEW view_name AS
SELECT column1, column2
FROM table_name
WHERE condition;
-- 查看视图
SHOW FULL TABLES WHERE TABLE_TYPE = 'VIEW';
-- 更新视图
ALTER VIEW view_name AS
SELECT column1, column2, column3
FROM table_name
WHERE condition;
-- 删除视图
DROP VIEW IF EXISTS view_name;
8.3 存储过程
-- 创建存储过程
DELIMITER //
CREATE PROCEDURE procedure_name(IN param1 INT, OUT param2 VARCHAR(100))
BEGIN
-- 存储过程体
SELECT column INTO param2 FROM table WHERE id = param1;
END //
DELIMITER ;
-- 调用存储过程
CALL procedure_name(5, @result);
SELECT @result;
-- 删除存储过程
DROP PROCEDURE IF EXISTS procedure_name;
9. 事务控制
9.1 事务基本操作
-- 开始事务
START TRANSACTION;
-- 执行SQL语句
INSERT INTO accounts (account_id, balance) VALUES (1, 1000);
UPDATE accounts SET balance = balance - 500 WHERE account_id = 1;
INSERT INTO transactions (account_id, amount) VALUES (1, -500);
-- 提交事务
COMMIT;
-- 或回滚事务
-- ROLLBACK;
9.2 设置保存点
-- 开始事务
START TRANSACTION;
-- 执行操作
INSERT INTO table1 VALUES (1, 'value');
-- 设置保存点
SAVEPOINT point1;
-- 执行更多操作
INSERT INTO table2 VALUES (2, 'value');
-- 回滚到保存点
ROLLBACK TO SAVEPOINT point1;
-- 提交事务（只提交保存点之前的操作）
COMMIT;
9.3 事务隔离级别
-- 查看当前事务隔离级别
SELECT @@TRANSACTION_ISOLATION;
-- 设置事务隔离级别
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE;
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
10. 实际应用案例
10.1 电子商务数据库设计
-- 创建数据库
CREATE DATABASE ecommerce CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
USE ecommerce;
-- 创建客户表
CREATE TABLE customers (
customer_id INT PRIMARY KEY AUTO_INCREMENT,
first_name VARCHAR(50) NOT NULL,
last_name VARCHAR(50) NOT NULL,
email VARCHAR(100) NOT NULL UNIQUE,
password VARCHAR(255) NOT NULL,
phone VARCHAR(20),
created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
INDEX idx_email (email),
INDEX idx_name (last_name, first_name)
);
-- 创建地址表
CREATE TABLE addresses (
address_id INT PRIMARY KEY AUTO_INCREMENT,
customer_id INT NOT NULL,
address_type ENUM('billing', 'shipping') DEFAULT 'shipping',
address_line1 VARCHAR(100) NOT NULL,
address_line2 VARCHAR(100),
city VARCHAR(50) NOT NULL,
state VARCHAR(50),
postal_code VARCHAR(20) NOT NULL,
country VARCHAR(50) NOT NULL,
is_default BOOLEAN DEFAULT FALSE,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE CASCADE,
INDEX idx_customer (customer_id)
);
-- 创建类别表
CREATE TABLE categories (
category_id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
description TEXT,
parent_id INT,
FOREIGN KEY (parent_id) REFERENCES categories(category_id) ON DELETE SET NULL
);
-- 创建产品表
CREATE TABLE products (
product_id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(100) NOT NULL,
description TEXT,
price DECIMAL(10, 2) NOT NULL CHECK (price > 0),
stock_quantity INT NOT NULL DEFAULT 0 CHECK (stock_quantity >= 0),
category_id INT,
created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
FOREIGN KEY (category_id) REFERENCES categories(category_id) ON DELETE SET NULL,
INDEX idx_category (category_id),
INDEX idx_name (name)
);
-- 创建订单表
CREATE TABLE orders (
order_id INT PRIMARY KEY AUTO_INCREMENT,
customer_id INT NOT NULL,
order_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
status ENUM('pending', 'processing', 'shipped', 'delivered', 'cancelled') DEFAULT 'pending',
shipping_address_id INT NOT NULL,
billing_address_id INT NOT NULL,
shipping_fee DECIMAL(10, 2) DEFAULT 0.00,
total_amount DECIMAL(10, 2) NOT NULL,
payment_method ENUM('credit_card', 'paypal', 'bank_transfer'),
notes TEXT,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE RESTRICT,
FOREIGN KEY (shipping_address_id) REFERENCES addresses(address_id) ON DELETE RESTRICT,
FOREIGN KEY (billing_address_id) REFERENCES addresses(address_id) ON DELETE RESTRICT,
INDEX idx_customer (customer_id),
INDEX idx_date (order_date)
);
-- 创建订单明细表
CREATE TABLE order_items (
order_id INT,
product_id INT,
quantity INT NOT NULL CHECK (quantity > 0),
unit_price DECIMAL(10, 2) NOT NULL,
PRIMARY KEY (order_id, product_id),
FOREIGN KEY (order_id) REFERENCES orders(order_id) ON DELETE CASCADE,
FOREIGN KEY (product_id) REFERENCES products(product_id) ON DELETE RESTRICT
);
-- 创建产品评价表
CREATE TABLE reviews (
review_id INT PRIMARY KEY AUTO_INCREMENT,
product_id INT NOT NULL,
customer_id INT NOT NULL,
rating TINYINT NOT NULL CHECK (rating BETWEEN 1 AND 5),
comment TEXT,
review_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
FOREIGN KEY (product_id) REFERENCES products(product_id) ON DELETE CASCADE,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE CASCADE,
UNIQUE KEY unique_review (product_id, customer_id),
INDEX idx_product (product_id)
);
-- 创建产品库存历史表
CREATE TABLE inventory_history (
id INT PRIMARY KEY AUTO_INCREMENT,
product_id INT NOT NULL,
quantity_change INT NOT NULL,
reason ENUM('purchase', 'sale', 'return', 'adjustment'),
reference_id INT,
changed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
FOREIGN KEY (product_id) REFERENCES products(product_id) ON DELETE CASCADE,
INDEX idx_product (product_id),
INDEX idx_date (changed_at)
);
-- 创建订单状态历史视图
CREATE VIEW order_status_history AS
SELECT
orders.order_id,
customers.email,
orders.status,
orders.total_amount,
orders.order_date
FROM orders
JOIN customers ON orders.customer_id = customers.customer_id;
-- 创建存储过程：处理订单
DELIMITER //
CREATE PROCEDURE process_order(IN order_id_param INT)
BEGIN
DECLARE current_status VARCHAR(20);
-- 获取当前订单状态
SELECT status INTO current_status FROM orders WHERE order_id = order_id_param;
-- 只处理待处理订单
IF current_status = 'pending' THEN
START TRANSACTION;
-- 更新订单状态
UPDATE orders SET status = 'processing' WHERE order_id = order_id_param;
-- 更新产品库存
UPDATE products p
JOIN order_items oi ON p.product_id = oi.product_id
SET p.stock_quantity = p.stock_quantity - oi.quantity
WHERE oi.order_id = order_id_param;
-- 记录库存变更
INSERT INTO inventory_history (product_id, quantity_change, reason, reference_id)
SELECT product_id, -quantity, 'sale', order_id_param
FROM order_items
WHERE order_id = order_id_param;
COMMIT;
SELECT 'Order processed successfully' AS message;
ELSE
SELECT CONCAT('Cannot process order. Current status: ', current_status) AS message;
END IF;
END //
DELIMITER ;
10.2 数据库维护操作
-- 分析表
ANALYZE TABLE customers, orders, products;
-- 检查表
CHECK TABLE customers, orders, products;
-- 优化表
OPTIMIZE TABLE customers, orders, products;
-- 修复表
REPAIR TABLE customers, orders, products;
10.3 常见查询和操作示例
-- 插入客户
INSERT INTO customers (first_name, last_name, email, password, phone)
VALUES ('John', 'Doe', 'john.doe@example.com', SHA2('password123', 256), '555-123-4567');
-- 插入产品
INSERT INTO categories (name, description) VALUES ('Electronics', 'Electronic devices and accessories');
INSERT INTO products (name, description, price, stock_quantity, category_id)
VALUES ('Smartphone X', 'Latest smartphone with advanced features', 699.99, 50, 1);
-- 创建订单（简化版）
INSERT INTO addresses (customer_id, address_type, address_line1, city, postal_code, country)
VALUES (1, 'shipping', '123 Main St', 'New York', '10001', 'USA');
INSERT INTO orders (customer_id, shipping_address_id, billing_address_id, total_amount, payment_method)
VALUES (1, 1, 1, 699.99, 'credit_card');
INSERT INTO order_items (order_id, product_id, quantity, unit_price)
VALUES (1, 1, 1, 699.99);
-- 处理订单
CALL process_order(1);
-- 复杂查询：查找畅销产品
SELECT
p.product_id,
p.name,
p.price,
SUM(oi.quantity) AS total_sold,
SUM(oi.quantity * oi.unit_price) AS total_revenue
FROM products p
JOIN order_items oi ON p.product_id = oi.product_id
JOIN orders o ON oi.order_id = o.order_id
WHERE o.order_date >= DATE_SUB(CURDATE(), INTERVAL 30 DAY)
GROUP BY p.product_id, p.name, p.price
ORDER BY total_sold DESC
LIMIT 10;
-- 创建每日销售报表视图
CREATE VIEW daily_sales AS
SELECT
DATE(o.order_date) AS sale_date,
COUNT(DISTINCT o.order_id) AS order_count,
SUM(oi.quantity) AS items_sold,
SUM(o.total_amount) AS total_revenue
FROM orders o
JOIN order_items oi ON o.order_id = oi.order_id
GROUP BY DATE(o.order_date)
ORDER BY sale_date DESC;
掌握数据库和表的基本操作是使用MySQL的基础。这些操作包括数据库的创建、修改和删除，表的设计、修改和管理，以及数据的增删改查。随着经验的积累，您可以进一步探索更高级的功能，如存储过程、触发器、视图和事务管理，以构建更复杂、更高效的数据库应用程序。
结语
感谢您的阅读！期待您的一键三连！欢迎指正！
