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Relational Database Technology

Objectives

This tutorial covers the following objectives:

  • Define and give an example of a relational database.
  • Identify table-key terms, including row, column, field, primary key, and foreign key.
  • Relate the importance of databases to everyday life.

Purpose

  • Databases are part of our everyday lives even though most of the time we don’t even think about them.
  • If you have ever made an airline reservation, used an ATM machine, or made a mobile-phone call, you’ve used a database.
  • In fact, many cities use intelligent traffic guiding system databases to control stoplights.
  • So the next time you’re waiting at a red light, it may be a database that is responsible for your delay!
  • In this lesson, you will learn more about databases and how they’re organized and created.

Some interesting databases found on the internet:

Relational Database Example

  • A relational database allows tables to be related by means of a common field.
  • As few as two tables can be considered a relational database if they share a common field.
Relational Databases
The “Region_id” column in this table is a common field with the “regions” table.
  • Realistically, databases used in business have many tables, each table sharing a common field with another table.
  • The “countries” table shown above is one of several tables in the Employees database and just one example of the many tables that will be used in this course.
  • To understand how important databases have become in today’s world, consider the following statistics:
    • Currently 20% of the world’s data resides in RDBMSs.
    • In the next two years, databases are expected to grow larger than 100 terabytes.
    • A database this big would be able to store 100,000 copies of the Encyclopedia Britannica or 200,000 hours of music or about 10 billion web pages.
  • Some of the top 10 world’s largest databases using the Oracle RDBMS are:
    • France Telecom, 29.2TB — a communications company (a TB is a terabyte equivalent to 1,000 gigabytes)
    • Amazon.com with, 13 TB — selling books and merchandise
    • The Claria Corporation,12TB — Internet behavioral marketing company tracking Internet user behavior

Review Key Terms

  • Let’s review the following key terms:
    • table — basic storage structure
    • column — one kind of data in a table
    • row — data for one table instance
    • field — the one value found at the intersection of a row and a column
    • primary key — unique identifier for each row
    • foreign key — column that refers to a primary-key column in another table

Properties of Tables

  • There are six properties of tables in a relational database:
    • Property 1: Entries in columns are single-valued
    • Property 2: Entries in columns are of the same kind
    • Property 3: Each row is unique
    • Property 4: Sequence of columns is insignificant
    • Property 5: Sequence of rows is insignificant
    • Property 6: Each column has a unique name

Accessing Data in an RDBMS

  • A relational database-management system (RDBMS) organizes data into related rows and columns.
  • To access the data in a database, you do not need to know where the data is located physically, nor do you need to specify an access route to the tables.
  • You simply use structured query language (SQL) statements and operators.

Communicating with Databases

  • Working with the database is very similar to calling up and talking to a friend on the phone.
    • First, you must choose a method to communicate (the phone).
    • Once connected, you ask your friend a question (a query).
    • In response to your question, your friend answers (return of data).
  • Pretty simple, and most of us are experts at this.
  • In this class, our method of communication with the database will be through Oracle Application Express.
  • When you ask a question using SQL, the application will return an answer.

Communicating With Databases

  • As shown in the diagram, communicating with an RDBMS is accomplished by entering a SQL statement in Oracle Application Express.
Communicating With Databases
  • The request is then sent to the Oracle Server (a database running on a computer), the request is processed and the data returned is displayed.
  • In very large database systems, many users, servers, and tables make up the RDBMS.

Categories of SQL Statements

  • SQL statements are grouped into several categories depending on the functions they perform.
  • During this course, you will learn how to use SQL to execute these statements.
  • The data retrieval statement retrieves data from the database using the keyword SELECT.

There are four main categories of SQL statements:

  • Data manipulation language (DML)
  • Data definition language (DDL)
  • Transaction control language (TCL)
  • Data control language (DCL)
  • Data manipulation language (DML)
    • DML statements begin with INSERT, UPDATE, DELETE, or MERGE and are used to modify the table data by entering new rows, changing existing rows, or removing existing rows.
  • Data definition language (DDL)
    • DDL statements create, change, and remove data structures from the database.
    • The keywords CREATE, ALTER, DROP, RENAME, and TRUNCATE begin DDL statements.
  • Transaction control language (TCL)
    • TCL statements are used to manage the changes made by DML statements.
    • Changes to the data are executed using COMMIT, ROLLBACK, and SAVEPOINT.
    • TCL changes can be grouped together into logical transactions.
  • Data control language (DCL)
    • DCL keywords GRANT and REVOKE are used to give or remove access rights to the database and the structures within it.

Terminology

Key terms used in this tutorial included:

  • Data control language (DCL)
  • Data definition language (DDL)
  • Data manipulation language (DML)
  • Field
  • Foreign key
  • RDBMS
  • Primary key
  • Relational database
  • Row
  • Table
  • Transaction control (TCL)

Summary

In this tutorial, you should have learned how to:

  • Define and give an example of a relational database
  • Identify table-key terms, including row, column, field, primary key, and foreign key
  • Relate the importance of databases to everyday life

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