SQL 将查询拆分为 start/end 并带有期望输出

Question

我有一个 table 有以下记录

ItemCode	Value
1	0.000
1	0.290
1	0.370
1	0.650
1	1.190
1	2.120
1	2.700
1	2.900
1	7.360
2	2.340
2	2.790
2	2.890
2	3.500
2	3.600
3	2.100
3	2.250
3	3.000

我想输出如下

ItemCode	BeginNum	EndNum
1	0.000	0.290
1	0.290	0.370
1	0.370	0.650
1	0.650	1.190
1	1.190	2.120
1	2.120	2.700
1	2.700	2.900
1	2.900	7.360
2	2.340	2.790
2	2.790	2.890
2	2.890	3.500
2	3.500	3.600
3	2.100	2.250
3	2.250	3.000

Answer 1

你想要lead():

select *
from (
    select itemcode, value as num, 
        lead(value) over(partition by itemcode order by value) as endnum
    from mytable 
) t
where endnum is not null

请注意，这会消除每组的最后一条记录，如示例数据所示。

Answer 2

你也可以这样做（如果你想要分组的最后一条记录，将'inner join'替换为'left outer join'）：

with tablewithrow as (
select f1.*, row_number() over(partition by f1.ItemCode order by (select null)) rang 
from mytable f1  
)

select f1.ItemCode, f1.Value BeginNum, f2.Value EndNum
from tablewithrow f1
inner join tablewithrow f2 on f1.ItemCode=f2.ItemCode and f1.rang=f2.rang - 1

SQL 将查询拆分为 start/end 并带有期望输出

SQL Query to split in start/end with desire output

sql-server

sql-server-2016