Terms containing need to know

Subject	English	Spanish
gen.	I know I was cheated, there is no need to rub it in	ya sé que me timaron, no hace falta que me lo restriegues
IT	"need to know"	necesidad de saber
IT	"need to know"	necesidad de conocer
gen.	need to know	necesidad de conocer
IT	need-to-know principle	"a los que necesiten saberlo"
gen.	there's no need for her to know	no hay necesidad de que se entere
gen.	We need to know from where the letter is	Necesitamos saber de donde procede  la carta
gen.	you need to know how to best combine these two flavours	hay que saber combinar estos dos sabores