Question

使用oracle SQL，在下面的数据集中，我想检查列B ='N'时，我希望它在列A中找到相同的ID，并比较列C中的行对于该ID。如果它们是相同的那么'Y'，如果不是那么'N'否则为空。

A   B   C       D
001 Y   Pizza   Pepperoni
002 Y   Pizza   Pepperoni
003 Y   Pizza   Pepperoni
003 N   Pizza   Sausage
004 Y   Pizza   Pepperoni
005 Y   Pizza   Pepperoni
005 N   Pizza   Sausage
005 N   Hamburger   Cheese

理想情况下，我会运行它来返回ID（列A）和case语句的结果，使其看起来像这样......

A      B
001    (Null)
002    (Null)
003    (Null)
003    Y
004    (Null)
005    (Null)
005    Y
005    N

任何人都可以提供您用来完成此操作的代码吗？

Answer 1

正如其他注释所述，根据您声明的规则，最后一行应该在B中具有值“N”。以下脚本根据规定的规则返回正确的结果，但与您的示例输出不匹配：< / p>

/* test data */ 
select '001' as a, 'Y' as b, 'Pizza' as c,       'Pepperoni' as d into testtable union all
select '002' as a, 'Y' as b, 'Pizza' as c,       'Pepperoni' as d union all
select '003' as a, 'Y' as b, 'Pizza' as c,       'Pepperoni' as d union all
select '003' as a, 'N' as b, 'Pizza' as c,       'Sausage' as d union all
select '004' as a, 'Y' as b, 'Pizza' as c,       'Pepperoni' as d union all
select '005' as a, 'Y' as b, 'Pizza' as c,       'Pepperoni' as d union all
select '005' as a, 'N' as b, 'Pizza' as c,       'Sausage' as d union all
select '005' as a, 'N' as b, 'Hamburger' as c,   'Cheese' as d
go

/* script */
select
   a
  ,case when b = 'Y' then null else
    case when c = lag(c, 1) over (partition by a order by c desc, d) then 'Y' else 'N' end
    end as b

from testtable
go


/* Results...*/

|-----+------|
| A   | B    |
|-----+------|
| 001 | NULL |
| 002 | NULL |
| 003 | NULL |
| 003 | Y    |
| 004 | NULL |
| 005 | NULL |
| 005 | Y    |
| 005 | N    |
|-----+------|

Oracle SQL - 比较列

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