Roza, do you care if a log/sign out was not performed for some reason? Maybe the db was not available in the latter part of one day and on the next day you wanted to finalize these records from a log book. If so, you will need to retrieve records where SignOut was Null (notice I'm supporting Ajax's suggestion that you need to read up on reserved words): http://allenbrowne.com/AppIssueBadWord.html
In that case, it might be SELECT * FROM usertable WHERE id=[enter id] AND SignOut = Null
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.