How do you select only the maximum version of a list of documents that have different versions in SQL?

Question

I have a database table that looks like this:

| ID | TITLE | VERSION | 
| 1  | file1 |    1    |
| 2  | file2 |    1    |
| 3  | file1 |    2    |
| 4  | file2          


        

Answer 1

Actually the best way to do this is using the ranking functions:

select id, title, version
from (select t.*
             row_number() over (partition by id order by version desc) as seqnum
      from t
     ) t
where seqnum = 1

The function row_number() is called an analytic function in Oracle. It assigns number 1, 2, 3 . . . to each row, based on the partitioning clause. The numbers start over at each id, and the largest version starts at 1.

Answer 2

Indeed, use a subquery to obtain the MAX version, grouped by TITLE, and then join the result of it with your table to obtain the ID:

SELECT t.*
FROM tbl t INNER JOIN 
     (SELECT title, MAX(version) version
      FROM tbl
      GROUP BY title
     ) max_t ON (t.version = max_t.version AND t.title = max_t.title);

DEMO.