MySQL数据类型与表操作全指南( 从基础到高级实践)

CREATE TABLE products (
    id INT PRIMARY KEY,
    price DECIMAL(10,2), -- 总10位，含2位小数
    quantity SMALLINT UNSIGNED -- 无符号小整数
);

CREATE TABLE users (
    username VARCHAR(50) NOT NULL,
    gender ENUM('Male','Female','Other'),
    interests SET('Music','Sports','Reading')
);

CREATE TABLE table_name (
    column1 datatype constraints,
    column2 datatype constraints,
    ...
编程    PRIMARY KEY (one_or_more_columns)
);

CREATE TABLE employees (
    emp_id INT AUTO_INCREMENT,
    first_name VARCHAR(20) NOT NULL,
    last_name VARCHAR(20) NOT NULL,
    birth_date DATE,
    hire_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    salary DECIMAL(10,2) CHECK (salary > 0),
    PRIMARY KEY (emp_id),
    UNIQUE (first_name, last_name)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

ALTER TABLE employees
ADD COLUMN email VARCHAR(100) AFTER last_name;

-- 修改数据类型
ALTER TABLE emplopythonyees
MODIFY COLUMN salary DECIMAL(12,2);
-- 重命名列
ALTER TABLE employees
CHANGE COLUMN birth_date date_of_birth DATE;

ALTER TABLE employees
DROP COLUMN hire_date;

ALTER TABLE orders
ADD PRIMARY KEY (order_id);

ALTER TABLE order_items
ADD CONSTRAINT fk_order
FOREIGN KEY (order_id) REFERENCES orders(order_id)
ON DELETE CASCADE;

ALTER TABLE users
ADD UNIQUE (email);

RENAME TABLE old_name TO new_name;
-- 或
ALTER TABLE old_name RENAME TO new_name;

TRUNCATE TABLE log_entries; -- 快速删除所有数据

DROP TABLE IF EXISTS temp_data;

CREATE TABLE customer_orders (  -- 使用蛇形命名法
    order_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
    customer_id INT UNSIGNED NOT NULL,
    order_date DATETIME DEFAULT CURRENT_TIMESTAMP,
    PRIMARY KEY (order_id)
);

CREATE TABLE payments (
    payment_id INT COMMENT '主键ID',
    amount DECIMAL(10,2) COMMENT '支付金额',
    payment_method ENUM('Credit','Paypal','Bank') 
        COMMENT '支付方式'
) COMMENT='支付信息表';

CREATE TABLE sensor_data (
    id INT AUTO_INCREMENT,
    sensor_id INT,
    reading_time TIMESTAMP,
    value FLOAT,
    PRIMARY KEY (id, reading_time)
) PARTITION BY RANGE (YEAR(reading_time)) (
    PARTITION p2020 VALUES LESS THAN (2021),
    PARTITION p2021 VALUES LESS THAN (2022),
    PARTITION p2022 VALUES LESS THAN (2023)
);

mysqldump -u root -p database_name > backup.sql

SHOW ENGINES; -- 查看支持的引擎

ANALYZE TABLE orders;
OPTIMIZE TABLE log_data;

-- 商品表
CREATE TABLE products (
    product_id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    description TEXT,
    price DECIMAL(10,2) UNSIGNED NOT NULL,
    stock INT UNSIGNED DEFAULT 0,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_name (name)
) ENGINE=InnoDB;
-- 订单表
CREATE TABLE orders (
    order_id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    user_id INT UNSIGNED NOT NULL,
    total_amount DECIMAL(12,2) NOT NULL,
    status ENUM('Pending','Paid','Shipped','Completed') DEFAULT 'Pending',
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    CONSTRAINT fk_user
        FOREIGN KEY (user_id) REFERENCES users(user_id)
        ON DELETE RESTRICT
) PARTITION BY HASH(order_id) PARTITIONS 4;
-- 订单明细表
CREATE TABLE order_details (
    detail_id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    order_id BIGINT UNSIGNED NOT NULL,
    product_id INT UNSIGNED NOT NULL,
    quantity SMALLINT UNSIGNED NOT NULL,
    price DECIMAL(10,2) NOT NULL,
    CONSTRAINT fk_order
        FOREIGN KEY (order_id) REFERENCES orders(order_id)
        ON DELETE CASCADE,
    CONSTRAINT fk_product
        FOREIGN KEY (product_id) REFERENCES products(product_id)
        ON DELETE RESTRICT
);

ALTER TABLE products AUTO_INCREMENT = 1000;

mysqlbinlog --start-datetime="2023-01-01 00:00:00" binlog.000001 | mysql -u root -p

pt-online-schema-change --alter "ADD COLUMN new_col INT" D=database,t=table --execute

ALTER TABLE orders ENGINE = InnoDB; -- 转换为InnoDB

CREATE TABLE invoices (
    subtotal DECIMAL(10,2),
    tax_rate DECIMAL(5,4),
    tax_amount DECIMAL(10,2) AS (subtotal * tax_rate) STORED,
    total DECIMAL(10,2) AS (subtotal + tax_amount) STORED
);

CREATE TABLE product_specs (
    product_id INT PRIMARY KEY,
    specs JSON
);
INSERT INTO product_specs VALUES (1, '{"colohttp://www.chinasem.cnr": "red", "weight": 500}');
SELECT specs->>"$.color" FROM product_specs;

-- 创建独立表空间
CREATE TABLESPACE ts1 ADD DATAFILE 'ts1.ibd' ENGINE=InnoDB;
CREATE TABLE large_table (
    id INT PRIMARY KEY
) TABLESPACE ts1;

CREATE TABLE accounts (
    id INT AUTO_INCREMENT PRIMARY KEY,
    balance DECIMAL(10,2) INVISIBLE
);
INSERT INTO accounts (id) VALUES (1); -- 必须显式指定可见列
SELECT * FROM accounts; -- 不显示balance列
SELECT id, balance FROM accounts; -- 显式查询