Question

I want to retrieve the last “VERSION” for each NID with the corresponding REVID in the following table:

+------+-------+-----+---------+----------+
| RHID | REVID | NID | VERSION |  ACTION  |
+------+-------+-----+---------+----------+ 
| 1    |   1   |  1  |    1    |  CREATE  |
+------+-------+-----+---------+----------+  
| 2    |   2   |  2  |    1    |  CREATE  |
+------+-------+-----+---------+----------+  
| 3    |   3   |  1  |    2    |  UPDATE  |
+------+-------+-----+---------+----------+  
| 4    |   4   |  1  |    3    |  UPDATE  |
+------+-------+-----+---------+----------+  
| 16   |   3   |  1  |    4    | ROLLBACK |
+------+-------+-----+---------+----------+

When I run:

SELECT a.nid, a.revID, MAX(a.version)
FROM `revision_history` a
GROUP BY a.nid; 

I expect the result to be:

+-----+-------+---------+
| NID | REVID | VERSION |
+-----+-------+---------+
|  1  |   3   |    4    |
+-----+-------+---------+
|  2  |   2   |    1    |
+-----+-------+---------+

Instead the results are:

+-----+-------+---------+
| NID | REVID | VERSION |
+-----+-------+---------+
|  1  |   3   |    4    |
+-----+-------+---------+
|  2  |   2   |    4    |
+-----+-------+---------+

---

Q. What is the appropriate query to obtain the results I expect?

NOTE:

This is to build a view (which, in MySQL, does not support subqueries).

Answer 1

try this:

select a.nid ,a.revID ,a.version
from   `revision_history` a
JOIN
      (SELECT nid,  MAX(version) as version
        FROM `revision_history` 
        GROUP BY nid)b
ON    a.nid=b.nid
AND   a.version=b.version

SQL fiddle demo