Remove tags via PHP

I have a website which requires me to delete the tags from a post programmatically from time to time. In effect, the tags become meaningless after the post function has been reached but the post can not be deleted from the system.

With this in mind, what I would like to do is load the tags and delete each from the wp_term_taxonomy and wp_term_relationships tables using PHP but before I go and write a series of SQL, I’m wondering if there’s a command built in to accomplish adding or removing tags from the post using PHP. Thanks.

Chris