Re: all the table values equal

>> It would help if you explain a little better the background of the
>> problem you're trying to solve.
>>
>> You want to find all the user IDs which have the same value on a
>> given time interval?
>>
>> Is my understanding correct?
>>
>
> Yes.
>
> Re-reading my post I saw that I could explain better!
>
> id_user | value | datetime
> 1 | 1 | xxx
> 1 | 2 | xxx+1
> 1 | -1 | xxx+2
> 2 | -1 | xxx
> 2 | -1 | xxx+1
> 3 | 4 | xxx
> 3 | 10 | xxx+1
> 3 | 4 | xxx+2
> 4 | 3 | xxx
> 4 | 3 | xxx+1
>
> So, the new question: how I can find which id_user has _all_ the "value"
> that I'm looking for? Say -1 as 3 and I want a id_user=2 for the first
> and for the latter id_user=4
>

OK, So, analysing your new question, the time interval is still important? 
Or no longer?
So writting your query in english : "I want all users that don't change 
"value" and their value is equal to x ?"

Or will you need to find all the users that don't change value with just one 
query? And the query would return something like

id_user | value
2 | -1
4| 3

?
Please advice me on this.

I am just trying to avoid misunderstanding your requirements and ending up 
with a query that doesn't really do what you need.

Best,
Oliver