A switching valve for an internal combustion engine, which has an adjustable compression ratio, namely to control a hydraulic oil flow particularly for an eccentric adjustment mechanism, having a control piston, which can be shifted by a switching mechanism similar to a ballpoint pen mechanism, wherein the control piston controls the hydraulic oil flow dependent on the switch position thereof, wherein the switching mechanism comprises at least one actuation element and a detent element, and wherein at least the control piston, the actuation element and the detent element are nested in each other so that they are implemented in a concentrically overlapping manner, at least in sections, when viewed in the shifting direction of the control piston.