Removing a variable from DB

[Knight]

When you have a database that holds a bunch of different variables (dynamics in my case) and you take one of the variable values and you set it to NULL, it takes the value of the var and sets it to NULL, but the variable itself still remains. The same is true if you use
DBName.variablename.clear();
and
DBName.variablename = "";

Does anyone know of a surefire way to remove a variable from a database NPC? There are ways such as using = ""; to make it appear as though the variable has been deleted (because variables with this value are not displayed in the NPCdump for that DB) when infact they still remain.

Thanks for the help!

- Knight