某些叶子的多个父亲的邻接列表?

I want to create a blog and in this blog we can have n-level category and I realy need to store a single post in several category. So i want adjancy list model with multiple parent for leaf nodes. As i think we should create 3 table for creating many to many join, and my table are

Categories-tbl

Id    cat-name    Parent-id

Leaf-Posts-tbl

Id    post-name 

Post-cat-tbl

post-id    cat-id

Now

I want all query we get from a simple adjacency list from this tables?

1.how can we get all leaf of parent?

2.get subtree childs

3.delete,update,insert...