April 2001
Beginner
792 pages
17h 51m
English
Content preview from Microsoft® SQL Server™ 2000 Programming by ExampleBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Self Joins
A self join is a special type of join, in which a certain table is joined to itself. Basically, in a self join, two copies of the same table are merged, generating a result set based on information stored in this table.
Generally, self joins are used to represent hierarchies in a table. For example, the Employees table has a column called reportsto, which has a foreign key pointing to the employeeid column in this table. Therefore, if you want to retrieve the manager of any employee, the Employees table must be joined to itself.
Listing 5.20 demonstrates how to extract information from this hierarchy represented in the Employees table, using a self join. Specifically, the query performs a self join to retrieve the name of Anne Dodsworth's ...
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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.
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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.