March 2001
Intermediate to advanced
640 pages
14h 9m
English
book
Sams Teach Yourself Transact-SQL in 21 Days, Second Edition
by Lowell Mauer, David Solomon, Bennett McEwan
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Day 6. Using Subqueries
One of the capabilities of SQL is to nest one SQL query within another. If you want to select data from one table based on a list of values, you could enter the WHERE condition values manually using an IN clause, or you could use a second SQL SELECT statement to get the values. When you use the result set from one query to supply another query's conditions, you are using a subquery. Subqueries enable you to perform in one step what otherwise would require multiple steps. In today's lesson, you will learn
How to write subqueries
Why to use subqueries: what they do and why they're useful
Subqueries returning a single value
Subqueries returning multiply values
Using the IN clause with a subquery
Correlated subqueries
Using WHERE ...
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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.