Flat battery

[Schbrenk]

Just bought 2010 2.0 to Passat and this morning could not get in ,battery totally flat .luckily the battery had enough charge to open back door ,but still could not open any other door. I tried the key in the lock but still wouldn't open door ( thought the key would work mechanicly on the door locks ) ,climbed over seats and opened bonnet ,replaced battery then opened doors. Surely there is a way to open the doors with the key ,without battery power, am I missing something