Question

下面是一张表：

ID＆amp; amp;当Role = Red

时捕获MAX值的行

ID    Role      HistID   Date       Style
1     Yellow     101      1/1/17     M
1     Red        101      1/2/17     F
1     Red        (Null)   1/5/17     C
2     Blue       101       5/1/17    a
2     Yellow     201       4/1/17    b
2     Red        301       5/5/17    C
3     Yellow     (Null)

引用以下行：

   ID    Role      HistID     Date     Style
   1     Red       (Null)     1/5/17    c
   2     Red        301       5/5/17    c

现在基于这些行应用条件。

WHEN HistID IS NOT NULL and Style = C THEN 'Assigned'
  ELSE'Unassigned'
END Status

输出：

ID    Role      HistID   Date       Style    Status
1     Yellow     101      1/1/17     M         Unassigned
1     Red        101      1/2/17     F         Unassigned
1     Red        (Null)   1/5/17     C         Unassigned
2     Blue       101       5/1/17    a         Assigned
2     Yellow     201       4/1/17    b         Assigned
2     Red        301       5/5/17    C         Assigned
3     Yellow     (Null)                        Unassigned

这里的答案不是很多，我想了解并学习应用MAX，Case Expression和Keep子句背后的语法。

Answer 1

使用窗口功能：

select t.*,
       (case when matches_flag > 0 then 'Assigned' else 'Unassigned' end) as status
from (select t.*,
             sum(case when role = 'Red' and histid is not null and style = 'C' then 1 else 0 end) over
                 (partition by id) as matches_flag
      from t
     ) t;

编辑：

实际上并不需要子查询。我只是认为它使逻辑更容易遵循。你可以这样做：

select t.*,
       (case when sum(case when role = 'Red' and histid is not null and style = 'C' then 1 else 0 end) over (partition by id) > 0
             then 'Assigned'
             else 'Unassigned'
        end) as status
from t;

MAX值行上的条件格式

1 个答案: