40 - 餐馆营业额变化增长

-- 方法一
SELECT 
    t.visited_on,
    sum(c.amount) amount,
    ROUND(sum(c.amount) / 7, 2) average_amount
FROM 
    customer c,
    -- 查出足够7天的数据日期
     (SELECT DISTINCT 
        visited_on
      FROM 
        customer
      WHERE 
        visited_on >=(SELECT ADDDATE(MIN(visited_on), 6) FROM customer)) t
WHERE 
    c.visited_on BETWEEN SUBDATE(t.visited_on, 6) AND t.visited_on
GROUP BY 
    t.visited_on;


-- 方法二
SELECT visited_on,
       amount,
      round(amount / 7, 2) average_amount
FROM (
        SELECT DISTINCT 
            visited_on,
            SUM(amount) OVER (ORDER BY visited_on RANGE INTERVAL 6 DAY PRECEDING) amount
        FROM 
            customer
    ) t
WHERE 
    -- 当前日期比最小值多6天及以上
    visited_on >=(SELECT ADDDATE(MIN(visited_on), 6) FROM customer);

-- 方法三
select 
    visited_on,sum_amount as amount,round(average_amount,2) as average_amount 
from
    # 分组的数据进行7日分组
    (
        select
            visited_on,
            sum(amount) over (order by visited_on rows 6 preceding) sum_amount,
            avg(amount) over (order by visited_on rows 6 preceding) average_amount
        from
        # 根据日期分组
            (
                select
                    visited_on,sum(amount) as amount
                from    
                    Customer
                group by    
                    visited_on
            )t1
    )t2
where datediff(visited_on,(select min(visited_on) from Customer))>=6