sql进阶教程,sql语句进阶,sql server进阶,sql进阶书籍,sqlserver进阶教程,sqlj
SQL进阶是指在掌握SQL基础知识的基础上，深入学习和应用SQL高级语法和技巧来完成更为复杂和高效的数据库操作和数据分析任务。

以下是SQL进阶的一些例子：

1. 使用联结（JOIN）进行多表查询


SELECT orders.order_id, customers.customer_name, orders.order_date
FROM orders
INNER JOIN customers ON orders.customer_id = customers.customer_id;


2. 使用子查询进行嵌套查询


SELECT customer_name, city, country
FROM customers
WHERE country IN (
SELECT country
FROM customers
GROUP BY country
HAVING COUNT(*) > 10
);


3. 使用窗口函数（WINDOW FUNCTION）进行排名和聚合计算


SELECT product_name, category, price,
RANK() OVER (PARTITION BY category ORDER BY price DESC) AS rank
FROM products;


4. 使用条件表达式（CASE EXPRESSION）进行数据转换和逻辑判断


SELECT order_id, order_date,
CASE
WHEN total_amount <= 1000 THEN 'low'
WHEN total_amount > 1000 AND total_amount <= 5000 THEN 'medium'
ELSE 'high'
END AS amount_level
FROM orders;


5. 使用存储过程（STORED PROCEDURE）进行程序化 SQL 编程和批量处理


CREATE PROCEDURE calculate_sales_tax (IN order_id INT, OUT sales_tax DECIMAL(10,2))
BEGIN
DECLARE sub_total DECIMAL(10,2);
SELECT SUM(quantity * price) INTO sub_total
FROM order_items
WHERE order_id = order_id;
SET sales_tax = sub_total * 0.1;
END;

CALL calculate_sales_tax(1001, @sales_tax);
SELECT @sales_tax AS sales_tax;