OK I’m so confused about composite primary keys. I know exactly what they are and what they do in theory, but I’m having trouble implementing them.
I know that multiple columns in a table make up a composite primary key. Problem is, how do I retrieve a composite primary key if it’s made up of so many columns? Or do I need an EXTRA column that combines the results of all the columns into a single string?
Please help >.<
Help very much appreciated!
P.S What’s the difference between “unique” and “primary” keys? I thought they were the same thing, and then someone says to me that I need to make my primary keys unique??? I thought by declaring a column a primary key in mySQL (i use auto-increment) puts a primary key constraint on the column … which ensures uniqueness!
