8
Displaying Data from Multiple Tables

CERTIFICATION OBJECTIVES

8.01 Write SELECT Statements to Access Data from More Than One Table Using Equijoins and Non-Equijoins/View Data That Generally Does Not Meet a Join Condition by Using Outer Joins

8.02 Join a Table to Itself by Using a Self-Join

8.03 Generate a Cartesian Product of All Rows from Two or More Tables

Two-Minute Drill

Q&A Self Test

This chapter reviews various types of joins. A join is a SELECT statement that retrieves data from two or more tables and connects that data together to produce a combined set of output. The SELECT statement specifies data in one table that is identical to data in another table. Tables that share common data elements that support joins are said to be “related” to each other. This is why a SQL database is called a “relational database management system”; joining tables is the whole purpose of SQL database systems.