How far awa is the constellation Sagittarius?

A "constellation" is better thought of as a direction away from the earth, not a physical object with a particular distance.  Saggitarius's nearest star is Ross 154 at 10 light-years.  It is too faint to be seen with the naked eye.  Saggitarius is also the direction of the core of the Milky Way galaxy, about 27 thousand light-years distant.