How to make improvements make happiness or unhappiness ?

[Gurn]

Hello,

I would like to make an improvement that give some happiness but i don't do anything good... Sounds not very complicated...

I try to alter the table via sql code, adding a happiness colomn :
ALTER TABLE Improvements ADD Happiness integer default 0;

the in a xml table i add a new improvement with <Happiness>2</Happiness>

Doesnt' work at all.
Somebody have an idea ?

Thank you