June 2004
Intermediate to advanced
848 pages
21h 28m
English
Content preview from Just Java™ 2
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Primary and Foreign Keys
It's one thing to put data into a database. You also need to be able to retrieve it on demand. The way we get data out of the database is to present it with the right unique identifier, known as a key. For example, in a database of vehicle license records, the VIN or Vehicle Identification Number will be the key to the table of vehicles.
Primary keys
Every table must and will have an attribute (or group of attributes together) that uniquely identifies every record. This attribute or group of attributes is called the primary key to the table. By “uniquely identify every record,” we mean that each record has a different value for that attribute or group of attributes. The primary key to our Person table is the ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.