SQL in 24 Hours, Sams Teach Yourself, 7th Edition

Hour 18

Using Subqueries to Define Unknown Data

What You’ll Learn in This Hour:

• ▶   Defining a subquery

• ▶   Justifying the use of subqueries

• ▶   Understanding examples of subqueries in regular database queries

• ▶   Using subqueries with data manipulation commands

• ▶   Using correlated subqueries to make subqueries specific

In this hour, you look at the concept of subqueries, a means by which you can perform additional queries of information from within the same SQL statement. Using subqueries enables you to easily perform complex queries that might rely on complex subsets of data in your database.

Defining Subqueries

A subquery, also known as a nested query, is a query embedded within the WHERE clause of another query to further restrict ...