SQL：提取某些条件下的记录

Question

I have rows in Oracle database table (having +2M records) and I want to extract records with some condition. The constraint is not setup on the table. Any help will be appreciated.

nif                 num_sum
--------------------------
123                   456
123                   456
123                   789   // => I want to select this
134                   600

Records having a nif with one or more same num_sum is allowed. But if a nif exists for two or more different num_sum s, I want to select that nif and num_sum . I showed the above records for explanation only.

I tried:

select distinct nif, num_sum
from sumcon
group by nif, num_sum
having count(distinct nif) > 1 

Answer 1

您不返回任何记录，因为nif只有1个不同的值，因此计数不大于1。

Answer 2

Given your description,

"Records having a nif with one or more same num_sum is allowed (a nif shouldn't be for two different num_sums)"

I think you want the following:

SELECT nif
  FROM sumcon
 GROUP BY nif
HAVING COUNT(DISTINCT num_sum) > 1;

First, in your original query DISTINCT is superfluous. Next, since you say there should not exist more than one distinct value of num_sum for a given value of nif , I think you want to group by nif and use COUNT(DISTINCT num_sum) . Now if you mean that a given value of num_sum should not exist for more than one unique value of nif , then you would want the following:

SELECT num_sum
  FROM sumcon
 GROUP BY num_sum
HAVING COUNT(DISTINCT nif) > 1;

If you need to get all the values of nif for which this is the case, then you would have to do something like this:

SELECT nif, num_sum FROM sumcon
 WHERE num_sum IN (
    SELECT num_sum
      FROM sumcon
     GROUP BY num_sum
    HAVING COUNT(DISTINCT nif) > 1
);

Hope this helps.

Answer 3

不确定是否正是您要的内容，但我希望它能对您有所帮助。

select nif, num_sum from sumcon group by nif, num_sum having count(1) > 1