Enemy circeling around Player

Yepp. The title says what I want to do. I want something to spin in a circle around something else. In greater detail I want an enemy that has detected the player in my FPS start creeping out the player by start circling around him while shooting instead of just riding towards him while shooting. I simply need to know a code to make something spin around something else. And it would help if it calibrates if the player is moving as well.

Any suggestions on how I could deal with this?