The spell table isn't designed with effect__base_value_# being linked to a spell effect. There are hundreds of effects but only 12 slots.
Warriors using defensive discs will certainly appreciate your update
You want something more like this (
not tested);
Code:
UPDATE spells_new
set effect_base_value1 = effect_base_value1 * 2,
max1 = max1 * 2
WHERE
effect_base_value1 < 0 and
effectid1 = [Spell ID to modify] and
(classes1 < 254 or classes2 < 254 or classes3 < 254 or classes4..(etc)....or classes16 <254);
Repeat for each of the 12 slots. Note that putting [spell id to modify] in the query will prompt you to specify a value to match against effectid1. In your case you'd enter the value for DD spells.