我可以将此销售比较放入单个列中吗？

Question

这是我的数据：

CREATE TABLE SALES (
    ts TIMESTAMP NOT NULL,
    name VARCHAR(50) NOT NULL,
    quantity INTEGER,
    price DECIMAL(2,2)
);

INSERT INTO SALES VALUES
    ("2017-02-08 13:38:02", "apple", 6, 4.38),
    ("2017-02-08 13:38:02", "banana", 10, 3.50),
    ("2017-02-08 13:38:02", "orange", 8, 2.98),
    ("2017-02-08 09:21:52", "banana", 6, 2.67),
    ("2017-02-08 09:21:52", "pear", 3, 2.00),
    ("2017-02-07 15:21:32", "apple", 6, 4.38),
    ("2017-02-07 15:21:32", "banana", 6, 2.67),
    ("2017-02-07 11:03:16", "orange", 8, 2.98),
    ("2017-02-07 11:03:16", "banana", 4, 1.17);

我想购买今天售出但昨天未售出的商品。

我可以使用以下方法将它们分成两列：

select
    name,
    SUM(case when strftime('%Y-%m-%d', sales_ts) = '2017-02-08' then quantity  else 0 end) as today,
    SUM(case when strftime('%Y-%m-%d', sales_ts) = '2017-02-07' then quantity  else 0 end) as yday
from sales
group by name
having yday = 0

结果：

| name | today | yday
---------------------
| pear |   3   |  0

但是我怎么能只得到 2 列，1 列用于名称，1 列称为 "sold_today_but_not_yday" 并具有 True/False 值？那可能吗？（最好不使用子查询）。

Answer 1

您可以使用 case:

select name,
       (case when SUM(case when strftime('%Y-%m-%d', sales_ts) = '2017-02-08' then quantity  else 0 end) > 0 and
                  SUM(case when strftime('%Y-%m-%d', sales_ts) = '2017-02-07' then quantity  else 0 end) = 0
             then 1 else 0
        end) as isTodayNotYesterday
from sales
group by name;

我可以将此销售比较放入单个列中吗？

Can I get this sales comparison into a single column?

sql

case-when