如何从增量年份值中获取旧值？

Question

我有两个表：

表 1:

|年份 |客户关系网络 |客户ID |帽 |
| 201910 | 14 | ABC1 | 12 |
| 201910 | 15 | ABC1 | 14 |
| 201820 | 25 | ABC1 | 15 |
| 201820 | 26 | ABC1 | 25 |
| 201810 | 43 | ABC1 | 10 |
| 201720 | 55 | ABC1 | 11 |

表 2:

|年份 |客户关系网络 |黑色 |
| 201910 | 14 | A1 |
| 201910 | 15 | A1 |
| 201820 | 25 | B2 |
| 201820 | 26 | B2 |
| 201810 | 43 | C3 |
| 201720 | 55 | C4 |
| 201720 | 95 | F5 |
| 201710 | 65 | D4 |

我想return:

来自表 1 的 CID 用于表 2 中的 CRN。如果 return 只有一个 CID 作为一年，表 1 中的同一个 CID 和表 2 中的同一个 BLCK 可能有多个 CRN。例如，对于 201910，CRN 14 和 15 具有相同的 CID ABC1 和相同的 BLCK A1。所以它应该 return ABC1 一次。
上一年 BLCK 值和来自表 1 的上限值之和，用于上一年在上面找到的 CID (ABC1) 的所有 CRN。 201820 总是在 201810 之后，Year 值总是递增为 201810、201820、201910、201920...例如，对于 201910，我应该得到 40 作为 Cap 的总和，因为 201820 年的 CID ABC1 有两个 CRN . 不确定 rownumber() 是否始终有效，因为我必须考虑减少 Year 以从当前值返回到先前值。

我正在使用 Oracle 11g。

预期输出：

|年份 | CID |CurrYear Cap|CurrYear BLCK|Last Year|LastYear Cap|LastYear BLCK|
|201910 | ABC1 | 26 | A1 | 201820 | 40 | B2 |

Answer 1

您可以使用 lag() 函数和 grouping 通过 year as

select "Year", "CID", "CurrYear Cap", "CurrYear BLCK",
       "Last Year", "LastYear Cap", "LastYear BLCK"
  from
    (
    select "Year", "CID", "CurrYear Cap", "CurrYear BLCK",
       lag("Year") over (order by "Year") as "Last Year", 
       lag("CurrYear Cap") over (order by "Year") "LastYear Cap",
       lag("CurrYear BLCK") over (order by "Year") "LastYear BLCK",
       row_number() over (order by "Year" desc) as rn
      from
        (
        with table1(Year, CRN, CID, Cap) as
        (
         select 201910 ,  14   ,  'ABC1'  , 12 from dual union all 
         select 201910 ,  15   ,  'ABC1'  , 14 from dual union all 
         select 201820 ,  25   ,  'ABC1'  , 15 from dual union all 
         select 201820 ,  26   ,  'ABC1'  , 25 from dual union all 
         select 201810 ,  43   ,  'ABC1'  , 10 from dual union all 
         select 201720 ,  55   ,  'ABC1'  , 11 from dual    
        )  ,
             table2(Year   ,  CRN  , BLCK) as
        (
         select 201910  ,  14   ,  'A1'   from dual union all
         select 201910  ,  15   ,  'A1'   from dual union all
         select 201820  ,  25   ,  'B2'   from dual union all
         select 201820  ,  26   ,  'B2'   from dual union all
         select 201810  ,  43   ,  'C3'   from dual union all
         select 201720  ,  55   ,  'C4'   from dual union all
         select 201720  ,  95   ,  'F5'   from dual union all
         select 201710  ,  65   ,  'D4'   from dual
        )
        select max(t1.year) as "Year", 
               max(t1.CID) as "CID", sum(t1.Cap) as "CurrYear Cap", max(t2.blck) as "CurrYear BLCK"           
          from table1 t1
          join table2 t2 on t1.year = t2.year and t1.crn = t2.crn 
         group by t1.year  
        ) 
    )
where rn = 1;

Year    CID   CurrYear Cap  CurrYear BLCK   Last Year   LastYear Cap  LastYear BLCK
------  ----  ------------  -------------   ----------  ------------  -------------- 
201910  ABC1       26             A1          201820         40             B2

如果最后的 where rn = 1 替换为 order by rn，则所有 "Year" 值的所有行都列在一个顺序中。

Demo

如何从增量年份值中获取旧值？

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