Question

请建议使用良好的SQL查询来查找库存差异的开始和结束日期

想象我在下表中的数据。

Sample_table

transaction_date  stock
2018-12-01          10
2018-12-02          10
2018-12-03          20
2018-12-04          20
2018-12-05          20
2018-12-06          20
2018-12-07          20
2018-12-08          10
2018-12-09          10
2018-12-10          30

预期结果应为

Start_date     end_date      stock
2018-12-01     2018-12-02     10
2018-12-03     2018-12-07     20
2018-12-08     2018-12-09     10
2018-12-10     null           30

Answer 1

这是差距和孤岛的问题。您可以为此使用row_numer和group by。

select  t.stock, min(transaction_date), max(transaction_date)
from (
   select row_number() over (order by transaction_date) -
      row_number() over (partition by stock order by transaction_date) grp,
      transaction_date,
      stock
   from data
) t
group by t.grp, t.stock

在下面的DBFIDDLE DEMO中，我也解决了最后一组的null值，但是查找连续行的主要思想是基于上述查询。

您可以检查this以获得此解决方案的说明。

Answer 2

您可以使用row_number()

在下面尝试

select stock,min(transaction_date) as start_date,
case when min(transaction_date)=max(transaction_date) then null else max(transaction_date) end as end_date
from
(
select *,row_number() over(order by transaction_date)-
row_number() over(partition by stock order by transaction_date) as rn
from t1
)A group by stock,rn

Answer 3

尝试将GROUP BY与MIN和MAX结合使用：

SELECT
  stock,
  MIN(transaction_date) Start_date,
  CASE WHEN COUNT(*)>1 THEN MAX(transaction_date) END end_date      
FROM Sample_table
GROUP BY stock
ORDER BY stock

Answer 4

您可以尝试使用LEAD，LAG功能，如下所示：

quiz

查找库存差异的开始和结束日期

4 个答案: