基于列值转换的窗口函数

Question

我有如下响应查询

dest	emp
893106	0
717205	1
888305	0
312301	1
645100	0
222001	0
761104	1

我想获得窗口函数来分隔如下行：

dest	emp
893106	0
717205	1

dest	emp
888305	0
312301	1

dest	emp
645100	0
222001	0
761104	1

所以每个窗口必须以 emp value = 0 开始并以 emp value = 1 结束。它必须检测列值的转换。

Answer 1

响应查询将按保持结果集中给定顺序的某个字段排序，以使查询正常工作。

您将在数据中查找当前值为 0 且先前值为 1 的模式，并开始一个新的 grp，如下所示。

这是一种方法。

create table t(id int, dest int, emp int);

insert into t 
select 1,893106,0 union all
select 2,717205,1 union all
select 3,888305,0 union all
select 4,312301,1 union all
select 5,645100,0 union all
select 6,222001,0 union all
select 7,761104,1;

commit;

with main_data
as (
select *,case when emp=0 and lag(emp) over(order by id)=1 then
                   1
                   else 0
         end as grp_val
  from t
    )
select *,sum(grp_val) over(order by id) as grp
  from main_data;

+====+========+=====+=========+=====+
| id | dest   | emp | grp_val | grp |
+====+========+=====+=========+=====+
| 1  | 893106 | 0   | 0       | 0   |
+----+--------+-----+---------+-----+
| 2  | 717205 | 1   | 0       | 0   |
+----+--------+-----+---------+-----+
| 3  | 888305 | 0   | 1       | 1   |
+----+--------+-----+---------+-----+
| 4  | 312301 | 1   | 0       | 1   |
+----+--------+-----+---------+-----+
| 5  | 645100 | 0   | 1       | 2   |
+----+--------+-----+---------+-----+
| 6  | 222001 | 0   | 0       | 2   |
+----+--------+-----+---------+-----+
| 7  | 761104 | 1   | 0       | 2   |
+----+--------+-----+---------+-----+

https://sqlize.online/sql/psql14/053971a469e423ef65d97984f9017fbf/