DB2® Universal Database for OS/390® Version 7.1 Certification Guide

Data Retrieval

SQL is based on mathematical principles, specifically set theory and relational algebra. The data is stored in the database as unordered sets of data records. SQL is a set-oriented language and many of its language elements are directly related to relational algebraic terms, such as PERMUTATION, PROJECTION, RESTRICTION, and JOIN.

A set of data is represented in a DB2 database as a table or a view and is stored in a DB2 table without regard to order. To retrieve data in a particular order, an ORDER BY phrase must be added to a SELECT statement. Similarly, if the data is to be grouped, then a GROUP BY phrase must be added to the statement.

Now, let's review the DB2CERT database design defined in the previous chapter and manipulate ...