Database Management Systems

Data base Systems organize the large volumes of data use in everyday transactions; data must be organized so that manager can use the information easily and quickly for decision making.

Data organization

The smaller concepts of data make available building blocks that can be combined to reproduce the original, in organized accessible form.

The Data Hierarchy

Data field is the smallest unit of data.

Record is a collection of related data fields.

File is a collection of related records.

Database is a collection of related files.

General definition Restrictive definition

Database

Table of rows and columns can be represented in a spreadsheet.

Relational database structure is conceptually similar to a collection of related tables.

Flat file is a table that does not have repeating columns; 1st normal form.

Normalization is a formal process for eliminating redundant data fields while preserving the ability of the database to add, delete, and modify records without causing errors.

Spreadsheet

Rows and columns can be represented in a spreadsheet because so many users are familiar with spreadsheet. The columns of the spreadsheet represent data field and the columns heading contain data field names.

Key in a table is a field (or combination of fields) that contain a value that uniquely identifies each record in the table.

Candidate key is a field that uniquely identifies each table row but is not the chosen key.

Relating tables is done through sharing a common field and the value of the field determines which rows in the tables are logically joined.

Database Structures

Database management system (DBMS) is a software application that stores the structure of the database, the data itself, relationships among data in the database, and forms and reports pertaining to the database.

Self-describing set of related data.

Hierarchical Database Structures

Hierarchical is formed by data groups, subgroups, and further subgroups; like branches on a tree.

Worked well with TPSs Utilized computer resources efficiently

Network allows retrieval of specific records; allows a given record to point to any other record in the database.

Database Structures

Relational is when the relationship between tables are implicit.

Physical relationship is when the database structure (hierarchical, network) rely on storage addresses.

Implicit relationship is when the database structure (relational) can be implied from the data.

A Relational Database Example

A database named Schedule has been created from tables used earlier in the chapter and some others.

The database is implemented in Microsoft Access 2002 (also known as Access XP).Databases break information into multiple tables because if information were stored in a single table, many data field values would be duplicated.

The Schedule Database

The example is implemented on Microsoft Access DBMS but would be similar on any relational DBMS product.

The COURSE table in Access is a list of data field values. The table itself had to be defined in Access before values were entered into the data fields.

Figure shows the definition of the Code field.

Abbreviation field values will be looked up from a list of values in the DEPARTMENT table.

single table of course and department fields before they were separated into different tables.

Creating a Database

Determine data that needs to be collected and stored is a key step.

Process-oriented approach

Define the problem. Identify necessary decisions. Describe information needs. Determine the necessary processing. Specify data needs.

Determine Data Needs

Enterprise modeling approach takes a broad view of the firm’s data resources; all areas are considered, and synergy of data resources between business areas can be leveraged.

Enterprise data model

Data Modeling Techniques

Entity-relationship diagrams (ERDs) is a graphical representation of data in entities and the relationships between entities.

Entity is a conceptual collection of related data fields.

Relationship is defined between entities.

One-to-one – 1:1 One-to-many – 1:M Many-to-many – M:N

Using the Database

Forms show one record at a time and can be used to add, delete, or modify database records.

Navigation Accuracy Consistency Filtering Sub forms

Using the Database

Reports are aggregated data from the database that are formatted in a manner that aids decision making.

Queries is a request for the database to display selected records.

Query-by-example (QBE) presents a standardized form that the user completes so the system can generate a true query.

Structured Query Language

Structured query language (SQL) is the code that RDBMSs use to perform their database tasks.

Method of choice for interacting with Web-based databases. Writing SQL statements are not difficult for most manager’s data needs.

Advanced Database Processing

On-line analytical processing (OLAP) allows data analysis similar to statistical cross-tabulation.

Data mining, data marts, and data warehousing focus on methodologies that offer users quick access to aggregated data specific to their decision-making needs.

Knowledge discovery analyzes data usage and data commonality among different tables.

Database Personnel

Database Administrator (DBA) is an expert in developing, providing, and securing databases; duties include:

Database planning; Database implementation; Database operation; Database security.

Database programmer writes code to strip and/or aggregate data from the database

High level of specialization and selection

End user generates reports and forms, post queries to the database, and use results from their database inquiries to make decisions that affect the firm and its environmental constituents.

Putting DBMS in Perspective

DBMS Advantages

Reduce data redundancy. Achieve data independence. Retrieve data and information rapidly. Improve security.

DBMS Disadvantages

Obtain expensive software. Obtain a large hardware configuration. Hire and maintain a DBA staff.