Docker image/container upgrade best practise

So simply create a file called docker-compose.yml with the following contents in the same folder as my Dockerfile, run the same command and I’m golden?

services:
  web:
    image: domoticz-php

It should update and overwrite my running container, yes? When I do, I’m left with a “domoticz-php” image created “x seconds” ago and an image called “” created 7 days ago (probably when I first fired up Docker). I can’t remove the image “” because it’s in use by a running container which is my current Domoticz container.

Oh btw, my container does have mappings to folders on the host (volumes?) and custom port settings.