Try like this;
ADD Load A, //which is key field
D //missing field(s)
Then save the application and go to front end then file--partial reload.
ADD :The ADD key word is used to reload the only new table(s).Called as partial reload.
It works like mapping will happen between the already loaded table and the newly field added table.
Your QVD is optimised.. when loading from a qvd, its not the same as loading from the database.
Load the existing fields from your qvd and just load the additional one from database into a new qvd. (Give it a new name or rename the old one first.
LOAD Key, Rest, Of, QVD FROM C:/YourQVD.qvd (qvd);
Join LOAD Key, OtherField;
SQL SELECT Key, OtherField
STORE YourQVD into C:/MyNewQVD.qvd (qvd);