Teradata方案

Question

给出：-

  

当DML_OPeration为D时，插入“ I”，则B = 0   删除“ D”，然后B将保留插入记录的A的值

条件：-

  

  
1. 如果COUNT OF'I'='D'计数，则我们不需要这些记录。例如：ID = 111
  
2. 查找最新的insert（'I'）DML_operation
  

    ID  A   B   DML_Operation
1   111 1   0   I
2   111 2   1   D
3   111 3   0   I
4   111 4   3   D
5   111 5   0   I
6   111 6   5   D
7   111 7   0   I
8   222 8   0   I
9   333 9   0   I
10  333 10  9   D
11  444 11  0   I
12  444 12  11  D
13  444 13  0   I
14  111 14  7   D
15  333 15  0   I
16  444 16  0   I
17  444 17  13  D

期望输出

ID  A   B   DML_Operation
-------------
222 8   0   I
333 15  0   I
444 16  0   I

我的逻辑不起作用

sel ID, Max(A) from xyz
group by ID
having count(c='I') <> COUNT(c='D')

Answer 1

如何使用case？

select ID, Max(A)
from xyz
group by ID
having sum( case when c = 'I' then 1 else 0 end) <> sum(case when c = 'D' then 1 else 0 end)

或者：

having sum(case when c = 'I' then 1
                when c = 'D' then -1
                else 0
           end) <> 0

Answer 2

您是否发现如下

    select ID, Max(A) from xyz
    group by ID
    having sum(case when c='I' then 1 else 0 end) <> sum(case when c='D' then 1 else 0 end)

Answer 3

这将找到所有'I'行而不匹配'D'行：

SELECT *
FROM mytab AS t1
WHERE DML_Operation = 'I'
AND NOT EXISTS
 ( SELECT *
   FROM mytab AS t2
   WHERE t2.id = t1.id
     AND t2.b = t1.a 
     AND DML_Operation = 'D'
 )