A primary key is a field used to uniquely identify every record in the database. Sometime primary keys are obvious, for example a car license plate could be used to uniquely identify cars. Often, ...

A primary key is a field used to uniquely identify every record in the database. Sometimes primary keys are obvious, for example a car license plate could be used to uniquely identify cars. Often, ...

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 with a ...

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 ...