How do I get more accurate results with SELECT MAX(id) WHERE id<=$id?

[Vigilante]

I've been doing this and similar queries in order to get the id number right before the one I'm inserting or just to get the latest id number but it seems to only be accurate some of the time. Why is this? How can I compensate for it?

Also, is it possible to select the max id and then select the name, title or whatever with the max id in the same query? If I did this, would be there be any (faster) way to seperate the two vars other then mysql_fetch_array?

[mikesgt2]

the id number right before the one I'm inserting

What exactly do you want to do? Would an auto_increment field sort this? or have i got the wrong end of the stick.