怎么写出上面的sql代码

编写上述SQL代码涉及的具体语法可能会因数据库管理系统（DBMS）的不同而有所差异，这里给出的是通用的示例，假设我们正在使用MySQL或PostgreSQL这样的关系型数据库：

1. 最高订单金额:

SELECT * FROM order_details 
ORDER BY amount DESC 
LIMIT 1;

2. 热门商品:

SELECT item_id, order_id, quantity, amount
FROM order_details
GROUP BY item_id, order_id
HAVING COUNT(*) >= 3
ORDER BY quantity DESC;

3. 客户限购查询:

SELECT customer_id, customer_name
FROM customers
WHERE total_quantity <= 10;

4. 订购多样化商品:

SELECT c.customer_id, c.customer_name, od.item_id, od.item_name, od.quantity, od.amount
FROM customers c
JOIN orders o ON c.customer_id = o.customer_id
JOIN order_details od ON o.order_id = od.order_id
GROUP BY c.customer_id, c.customer_name, od.item_id, od.item_name, od.quantity, od.amount
HAVING COUNT(DISTINCT od.item_id) >= 3;

5. 销售员业绩:

SELECT sp.salesperson_id, sp.salesperson_name, SUM(od.amount) as total_sales
FROM salespeople sp
JOIN orders o ON sp.salesperson_id = o.salesperson_id
JOIN order_details od ON o.order_id = od.order_id
GROUP BY sp.salesperson_id, sp.salesperson_name
ORDER BY total_sales DESC
LIMIT 1;

其他查询可以类似地构造，需要注意SQL语法的细微差别以及表之间的关联。如果你的数据库不是基于SQL，那么查询可能会有不同的结构。记住，在实际应用中，确保正确连接表并使用合适的函数和关键字。