September 2015
Beginner
288 pages
5h 39m
English
Content preview from Oracle PL/SQL in 10 Minutes, Sams Teach Yourself
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Lesson 14. Working with Subqueries
In this lesson, you’ll learn what subqueries are and how to use them.
Understanding Subqueries
SELECT statements are SQL queries. All the SELECT statements you have seen thus far are simple queries: single statements retrieving data from individual database tables.
Query
Any SQL statement. However, the term is usually used to refer to SELECT statements.
SQL also enables you to create subqueries: queries that are embedded into other queries. Why would you want to do this? The best way to understand this concept is to look at a couple of examples.
Filtering by Subquery
The database tables used in all the lessons in this book are relational tables. (See Appendix A, “The Example Tables,” for a description of ...
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