May 2008
Beginner
504 pages
8h 34m
English
Content preview from Sams Teach Yourself SQL in 24 Hours, Fourth EditionBecome 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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Chapter 14. Using Subqueries to Define Unknown Data
During this hour, you are presented with the concept of using subqueries to return results from a database query more effectively.
The highlights of this hour include:
What a subquery is
The justifications of using subqueries
Examples of subqueries in regular database queries
Using subqueries with data manipulation commands
Embedded subqueries
What Is a Subquery?
A subquery, also known as a nested query, is a query embedded within the WHERE clause of another query to further restrict data returned by the query. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. Subqueries are used with the SELECT, INSERT, UPDATE, and DELETE ...
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