sql语句大全实例教程

SQL（Structured Query Language）是一种用于管理关系型数据库的标准编程语言。下面是一些常用的 SQL 语句和示例教程：

1. 创建表格

CREATE TABLE customers (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    email VARCHAR(50)
);

2. 插入数据

INSERT INTO customers (id, name, email) VALUES
(1, 'John', 'john@example.com'),
(2, 'Mary', 'mary@example.com'),
(3, 'Bob', 'bob@example.com');

3. 查询数据

SELECT * FROM customers;

4. 更新数据

UPDATE customers SET email = 'john@gmail.com' WHERE id = 1;

5. 删除数据

DELETE FROM customers WHERE id = 3;

6. 连接表格

SELECT 
    customers.name, 
    orders.product_name, 
    orders.price 
FROM 
    customers 
INNER JOIN 
    orders ON customers.id = orders.customer_id;

7. 分组数据

SELECT 
    customers.name, 
    COUNT(orders.id) AS num_orders, 
    SUM(orders.price) AS total_spent 
FROM 
    customers 
INNER JOIN 
    orders ON customers.id = orders.customer_id 
GROUP BY 
    customers.name;

8. 排序数据

SELECT * FROM customers ORDER BY name ASC;

9. 聚合数据

SELECT AVG(price) AS avg_price FROM orders;

以上是一些常用的 SQL 语句和示例教程，希望对你有所帮助！