mysql from里有子查询

SELECT 
    c.customer_id,
    c.customer_name,
    order_summary.total_orders,
    order_summary.total_amount
FROM 
    customers c,
    (
        SELECT 
            customer_id,
            COUNT(*) AS total_orders,
            SUM(amount) AS total_amount
        FROM 
            orders
        GROUP BY 
            customer_id
    ) AS order_summary
WHERE 
    c.customer_id = order_summary.customer_id;

SELECT 
    c.customer_id,
    c.customer_name,
    COUNT(o.order_id) AS total_orders,
    SUM(o.amount) AS total_amount
FROM 
    customers c
JOIN 
    orders o ON c.customer_id = o.customer_id
GROUP BY 
    c.customer_id, c.customer_name;

SELECT 
    customer_id,
    customer_name
FROM 
    customers
WHERE 
    customer_id IN (
        SELECT 
            customer_id
        FROM 
            orders
        WHERE 
            status = 'completed'
    );