A screw assembly includes a screw member, a rotating member, and an installation member. The screw member includes a cap portion and a body connected to the cap portion. The installation member defines an installation slot and includes an elastically deformable latching portion. The rotating member includes a mounting portion. The installation member is secured to the body, the mounting portion is received in the installation slot, and the elastically deformable latching portion engages the mounting portion between the cap portion and the latching portion, to prevent the rotating member from rotating relative to the screw member and the installation member.