Question

I have a table of (700+ rows) with the following format:

id | session | win
------------------
 1     1122     1
 2     1122     1
 3     1122     1
 4     4559     1
 5     4559     1
 6     4559     1
 7     4559     1
 8     4559     1

Where win is either 1 or 0.
And session is not unique.

I want to update the group of rows that have the same session, and have all their win field set to 0 except for 1.

Goal:

id | session | win
------------------
 1     1122     1
 2     1122     0
 3     1122     0
 4     4559     1
 5     4559     0
 6     4559     0
 7     4559     0
 8     4559     0

Answer 1

Taking into consideration MySQL’s horrible syntax to perform updates, the only way I can think of doing this is:

update t set win = 0
where id not in (
    select id from (
        select min(id) id from t
        group by session
    ) s
);

It’d also possible to join instead of group by but I think a group by in this case would be faster.