4_Concepts_of_DB_methodical_l1_v1

Basic Concepts

A database is just what the name implies, a base collection of data.  The data is organized in some manner so that the information contained within the database can be easily retrieved.  Some of the simple databases that you might be familiar with are things like phone books or rolodexes.  As data processing has become more sophisticated, so have methods for collecting, storing and retrieving information.  Databases have become the cornerstone for an overwhelming amount of the computing environment in existence.

Basic Database concepts for the opening section

Field (Column): a single piece of information.  Could be a name, or a number.  In some cases, it may even be a null or empty value.

Record (Row): a collection of related fields.  A number of pieces of information that relate to the same object.  For example:  If you keep records on an employee, you might have their name, address, social security number, phone number, etc…Each piece of the information relates back to one employee.  This would be the employee’s record.

Table (File): a collection of related records.  If you put all the employee records together, you have a table of employees.

Database: a collection of tables.  If you were keeping the company records, you might have a table for employees, a table for customers, and another for sales records.  All these tables would be combined as a database.

Relational Database: a collection of related tables.  The difference between a database and a relational database is in the way the tables are constructed.  If you were keeping the company records on a series of Excel spreadsheets, you would have just a database.  You could pull information from each table, but you wouldn’t have the ability to use information from one spreadsheet as a basis for asking questions about the information contained on another sheet.  In a relational database, the tables are constructed so that there is a logical link between them.  Based on the information that’s found in one table, you can follow this link and get relevant information from another table.

Example: Relational Database versus Non-Relational Database

In order to build and maintain a relational database, you use a relational database management system.

A Relational Database Management System (DBMS) – software that allows users to create, maintain, and query your data in the related tables.

 Some common DBMS programs are Access, Microsoft SQL Server, Oracle, FoxPro, RBase, and Paradox

Common features of a DBMS

• Creating and Adding of Data Structures
• Query language
• Reporting facility
• Security, Control, Backup, and Disaster Recovery

To explore aspects of database management, the tool that will be used in this class is Microsoft Access 2000.  This is one of a series of iterations of MS Access. 

 The previous versions of Access were

• Access 2
• Access 7 (Office 95)
• Access 8 (Office 97)
• Access 2000
• Most recently, the newest iteration, Access XP was introduced as part of the Microsoft Office suite.

Difference between Access and large commercial databases

Access is a very powerful program, when used in the way that it is intended to be used.  Access is what’s known as a desktop database.  This means that it is designed for small-scale applications (50,000 records or less) and no more than 2 or 3 concurrent users (no more than 2 or 3 people trying to use the database at the same time).  When these parameters are exceeded, the database may become slow and unresponsive.

Access does not have very strong security or disaster recovery facilities.  If you are working on a database that requires these features, you may want to consider a more robust DBMS such as Oracle or SQL Server.

An Access database is allowed to be 1 Gigabyte in size and contain 32,768 Objects.  Objects being tables, queries, reports, etc…everything is kept in a single container.  This is the database file or mdb (Microsoft database).  All the files will be saved with the file extension mdb.

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