I have the following DB: Posts which have an Id, Tags also with Id, and TagsToPosts table which have TagsToPosts.PostId => Posts.Id and TagsToPosts.TagId => Tags.Id FK relations. I need to delete multiple items from TagsToPosts in following way. I'm creating IList<Tag> newTagsby parsing a string. Each tag have it's name. I want to delete all TagsToPosts items pointing to single post (TagsToPosts.PostId == mypostid) and which points to Tag with name which not in mynewTags.

For instance I have one post with Id = 1, three tags: 1 => "tag1", 2 => "tag2", 3 => "tag3"And ManyToMany relations table TagsToPosts: 1 => 1, 1 => 2, 1 => 3 So all three tags are linked to my post. After that I'll create a new IList<Tag> newList = new List<Tag>() by parsing a string. newList contains: 0 => "tag1", 0 => "tag2". Now I want to remove third relation from table TagsToPosts because my new list of tags doesn't contain tag with name "tag3". So I need to find a difference. I know I can find similar items using JOIN but how to find difference?

I want this to happend in one DB query without iterating over each item to delete it.