Question

Difficult to put down in words, so assuming this example table:

 | id | col1 | col2 |  -------------------- | 1  |  aa  |  12  | | 2  |  aa  |  12  | | 3  |  bb  |  13  | | 4  |  cc  |  13  | 

I would like a query which selects rows 3 & 4 or even just the value 13

So something like checking this assumption: ‘all values of col2 which are the same should map one value of col1’

I’ve been checking by doing a ‘group by’ and row count for each column in separate queries and comparing, but it would be nice to be able to pick out offending rows

A query or pl/sql procedure would be fine

Answer 1

To get just ’13’:

select col2 from mytable group by col2 having count(distinct col1) > 1; 

To get the rows:

select * from mytable where col2 in ( select col2   from mytable   group by col2 having count(distinct col1) > 1 );