Oracle 12c-过滤具有多个值的记录

Question

I have 2 columns:

DEPT_ID number; DEPT_SUB_ID varchar2(5);

I want to find all the DEPT_ID's which have more than one unique value for DEPT_SUB_ID.

How can this be done?

Answer 1

I would use:

select dept_id
from x
group by dept_id
having min(dept_sub_id) <> max(dept_sub_id);

In many cases, two simple aggregations (such as min() or max() ) have better performance than a count(distinct) .

Answer 2

Simply use count with distinct.

select dept_id,count(distinct dept_sub_id) 
from dept 
group by dept_id 
having count(distinct dept_sub_id) > 1;

Answer 3

select dept_id, count(distinct dept_sub_id)
from x
group by dept_id
having count(distinct dept_sub_id) > 1

The keys here are count(distinct) which counts the distinctly different dept_sub_id's within the dept_id

Group by, obviously groups the counts by dept_id

having is like a "where" ran after the group-by does its grouping.