SQL从子查询中选择

Question

I have an issue selecting from a subquery with this small demo data for example:

ID          CLASS_ID               PROP          STATUS        ROW     SELECTED    STEP
12345679    1312            0         21           3       07-FEB-14    1
12345679    1312            0         21           1       26-FEB-14    -1

I want to get all the information (each column), the sql below works ok

SELECT ID,CLASS_ID,min(SELECTED) FROM ( SELECT... ) GROUP BY ID,CLASS_ID

ID          CLASS_ID             SELECTED   
12345679    1312                07-FEB-14   

But if I want other columns I must add them to the group statement else I get "not a group statement" thus making it obsolete, any ideas?

Answer 1

You want to use the analytic function row_number() :

select ID, CLASS_ID, PROP, STATUS, ROW, SELECTED  
from (select s.*, row_number() over (partition by id, class_id
                                     order by selected desc) as seqnum
      from (<subquery>) s
     ) s
where seqnum = 1;

Answer 2

you want to get the minimum of selected column based on group by ID and class_id with all other columns then you can use MIN() over partitioned by function -

SELECT ID,
       CLASS_ID,
       min(SELECTED) over (partition by ID,CLASS_ID order by 1) , 
       col1 ...
FROM ( SELECT... )