I would not recommend via a direct SQL command. Possible yes but not straight forward. There are lots of objects and links to ensure are updated correctly and you run risk of corrupting database.
The standard UI tools can handle hundreds or thousands of objects at a time. I would just do it that way and be safe. It will take some time but you can run this in the background. Make sure in the collector you only grab objects you select and move all versions. This way it will not moving these you do not want. It should be easy to burn down list from one context as they move to the other. Remember to watch out for publishing since depending on how its configured, moves can cause a republish job.
