How to force an iphone 4 to turn on?

My iphone 4 turned off for no reason, and it won't turn back on! Is there a way to turn it on with out losing its whole data base? Thank!

Not sure everyone talks about IPhone s Pads Etc as if its a different technology to everything else.

Fact is its the same as any other phone and a common solution is to just take the battery out for about 30 seconds and put it back in to reset hope that works.

About simon's answer, You can't Remove the battery from any Apple Devices Duhh.

OK, long press the lock button ( right top) for maybe 30 seconds and wait and see. If that doesn't work, put your iphone aside for maybe 1day, don't bother with it. After that, try charging it and see what happeneds. You can always find help from the Apple Genius Bar or other official Apple device sellers if that doesn't work.