Reference question and auto increment

I am trying to understand references in tables and using primary keys with auto increment option as a reference to all tables: What is the best way to reference other tables? I have three tables: menus, categories, and links. I also have an ID field in each table that uses the autoincrement

Output from select is not what expected

 I have three tables in a database called menus and I have added 2 records to each table so 2*3=6 records. Why is it when I do a "select * from table1, table2, table3" I get 8 records back when there are only 2 records in each table? What am I doing wrong? Some of the fields are references if

Inserting data to multiple table at once

 How do I insert data into multiple tables without having to use multiple insert statements? Can I just do Insert into table1 (data) table2 (data) table3 (data) or do I have to use seperate INSERT statements for each table? I would like to add all at once from web page form $query =