sql 查找满足条件后 3 天内的记录

Question

我正在尝试查找在事件发生之前的日期范围内存在的所有记录。在我下面的 table 中，我想提取从 switch 字段从 0 变为 1 时起 3 天或更短时间的所有记录，按日期排序，按产品分区。我的解决方案不起作用，它包括第一个应该跳过的记录，因为它在 3 天 window 之外。我正在扫描包含数百万条记录的 table，有没有办法在保持我想要的结果的同时减少 complexity/cost？

http://sqlfiddle.com/#!18/eebe7

CREATE TABLE productlist
    ([product] varchar(13), [switch] int, [switchday] date)
;

INSERT INTO productlist
    ([product], [switch], [switchday])
VALUES
    ('a', 0, '2019-12-28'),
    ('a', 0, '2020-01-02'),
    ('a', 1, '2020-01-03'),
    ('a', 0, '2020-01-06'),
    ('a', 0, '2020-01-07'),
    ('a', 1, '2020-01-09'),
    ('a', 1, '2020-01-10'),
    ('a', 1, '2020-01-11'),
    ('b', 1, '2020-01-01'),
    ('b', 0, '2020-01-02'),
    ('b', 0, '2020-01-03'),
    ('b', 1, '2020-01-04')
;

我的解决方案：

with switches as (
SELECT
  *,
  case when lead(switch) over (partition by product order by switchday)=1
    and switch=0 then 'first day switch'
    else null end as leadswitch
  from productlist
  ),
 switchdays as (
   select * from switches
   where leadswitch='first day switch'
   )
 select pl.*
 ,'lead'
 from productlist pl
 left join switchdays ss
 on pl.product=ss.product
 and pl.switchday = ss.switchday
 and datediff(day, pl.switchday, ss.switchday)<=3
 where pl.switch=0

期望的输出，捕获从 0 到 1 的转换后 3 天内发生的记录，对于每个产品，按日期排序：

product switch  switchday   
a   0   2020-01-02  lead
a   0   2020-01-06  lead
a   0   2020-01-07  lead
b   0   2020-01-02  lead
b   0   2020-01-03  lead

Answer 1

如果我没理解错的话，你可以用lead()两次：

select pl.*
from (select pl.*,
             lead(switch) over (partition by product order by switchday) as next_switch_1,
             lead(switch, 2) over (partition by product order by switchday) as next_switch_2
      from productlist pl
     ) pl
where switch = 0 and
      1 in (next_switch_1, next_switch_2);

Here 是一个 db<>fiddle.

编辑（基于评论）：

select pl.*
from (select pl.*,
             min(case when switch = 1 then switchdate end) over (partition by product order by switchdate desc) as next_switch_1_day
      from productlist pl
     ) pl
where switch = 0 and
      next_switch_one_day <= dateadd(day, 2, switchdate);

sql 查找满足条件后 3 天内的记录

sql that finds records within 3 days of a condition being met

sql

sql-server

window-functions