SQL如何查询总计和小计

Question

我有一个如下所示的表，其中存储了 day、order_id 和 order_type。

select day, order_id, order_type
from sample_table

<头>

天	order_id	订单类型
2021-03-01	1	离线
2021-03-01	2	离线
2021-03-01	3	在线
2021-03-01	4	在线
2021-03-01	5	离线
2021-03-01	6	离线
2021-03-02	7	在线
2021-03-02	8	在线
2021-03-02	9	离线
2021-03-02	10	离线
2021-03-03	11	离线
2021-03-03	12	离线

以下是所需的输出：

<头>

天	total_order	num_offline_order	num_online_order
2021-03-01	6	4	2
2021-03-02	4	2	2
2021-03-03	2	2	0

有人知道如何查询以获得所需的输出吗？

Answer 1

您需要对数据进行透视。在 Vertica 中实现条件聚合的一种简单方法是使用 :::

select day, count(*) as total_order,
       sum( (order_type = 'online')::int ) as num_online,
       sum( (order_type = 'offline')::int ) as num_offline
from t
group by day;

Answer 2

使用 case 和 sum：

select day, 
    count(1) as total_order
    sum(case when order_type='offline' then 1 end) as num_offline_order,
    sum(case when order_type='online' then 1 end) as num_online_order
from sample_table
group by day
order by day

Answer 3

您还可以使用 count 来聚合非空值

select 
    day, 
    count(*) as total_order, 
    count(case when order_type='offline' then 1 else null end) as offline_orders,
    count(case when order_type='online' then 1 else null end) as online_orders 
from sample_table 
group by day 
order by day;