Group only the adjacent rows

Question

hi i have a table like this:

notifies

id,user_id
1,3
2,3
3,4
4,5
5,6
6,3
7,4
8,4
9,3
10,3

I have to create a query that group only the adjacent rows

So, the result of this example should be:

user_id
3
4
5
6
3
4
3

How can i do that? thanks

Answer 1

SELECT  user_id
FROM    notifies n
WHERE   NOT
        (
        SELECT  user_id
        FROM    notifies ni
        WHERE   ni.id < n.id
        ORDER BY
                id DESC
        LIMIT 1
        ) <=> user_id