For Higher Computing Science, revise the use of primary and foreign keys and the difference between flat file and relational databases.

Duplicate and Ignore on MySQL Inserts. MySQL table primary keys and unique indexes prevent multiple rows with the same index from being added to the table. If you try to insert a duplicate row ...

I'm working on a web app, and it part of it, there is a very simple database-driven file/document manager. As a file manager, there is the possibility of sub-folders. So in the DB, I have the ...