Question

I have a few simliar tables. I need to select them through *.
I would like to get a list of the rows where revnr is the highest one within each docid.

My problem here is that I don’t know how to get the local max(revnr) for each docid.

I am using MySQL but I’d prefer a general sql solution.

Thanks!

Answer 1

You can get the latest value of revnr for each docID in a subquery then the result of that will then join to the table itself.

SELECT  a.*
FROM    tableName a
        INNER JOIN
        (
            SELECT  docID, MAX(revnr) max_val
            FROM    tableName
            GROUP   BY docID
        ) b ON  a.docID = b.docID AND
                a.revnr = b.max_val

for better performance, add an INDEX on both columns: docID and revnr

ALTER TABLE tableName ADD INDEX (docID, revnr);