I try to explain in a better way:

I've build a serch page following your indications and it works well.
Unfortuntely teh search works in a table with 200.000 records and to load everything is very hard.

So that I've passed a parameter to search to ari data table changing the query from this
select
denominazione,
cod_fiscale,
num_avviso,
importo
from
cb6crm_contribuenti
where
denominazione ={$REQUEST:sSearch|empty:''}

to that:

select
denominazione,
cod_fiscale,
num_avviso,
importo
from
cb6crm_contribuenti
where
denominazione like {$REQUEST:sSearch%|empty:''}

but I probably make a mistake with the sysntax: Could you pleasae help me?

I fondi the Solutions by myself

select
denominazione,
cod_fiscale,
num_avviso,
importo
from
cb6crm_contribuenti
where
denominazione like concat ({$REQUEST:sSearch},'%')

Now it works perfectly