Sql Excel : SQL Queries

This section provides the third perspective on SQL, an introduction to the SQL
querying language. The querying part of SQL is the visible portion of an iceberg
whose bulky mass is hidden from view. The hidden portion is the data
management side of the language—the definitions of tables and views, inserting
rows, updating rows, defining triggers, stored procedures, and so on. As data
miners and analysts, our goal is to exploit the visible part of the iceberg, by
extracting useful information from the database.
SQL queries answer specific questions. Whether the question being asked is
actually the question being answered is a big issue for database users. The
examples throughout this book include both the question and the SQL that
answers it. Sometimes, small changes in the question or the SQL produce very
different results.