Chapter 6.2 - Developing Business Systems with Databases

Chapter 6.2 - Developing Business Systems with Databases -...

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Chapter 6 Part 2
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Hierarchy of Data File Management System vs. Database System Designing a Relational Database Creating an Entity-Relationship Diagram (ERD) Transferring an ERD into Database Tables
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Bit (a binary digit): a switch that is either on or off. Byte: group of 8 bits, represents a single character. Field: name, number, or characters that describe an aspect of a business object or activity. Record: collection of related data fields. File (or table): collection of related records. Database: a collection of integrated and related files.
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Sales Order Program Customer Billing Payroll Sales Department Accounting Department Users Custom er File Order er Employ ee
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Data Redundancy different systems have separate copies of similar or identical data Wastes storage space Increases chances for data inconsistencies and errors Data Isolation Limited data sharing Different/proprietary file formats Different data types No centralized control of data Requires more time spent on programming to accomplish tasks
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Sales Order Program Customer Billing Payroll Sales Department Accounting Department Users Metada ta Order, Custom er, Employ ee Data Database Manageme nt System DBMS manages data resources like an operating system manages hardware resources
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Minimize data redundancy Data is located in only one location Minimize data isolation Easier to share data when in one location Increase data security Built-in security features Increase data integrity Built-in validation and integrity capabilities Increase data independence Data stored separately from applications requires less applications maintenance when data changes
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The Relational database represents data as a collection of Tables . Each table stores data about one part of the system To be considered relational a database must follow certain specifications: Columns of the table are different Fields Rows of the table represent different Records No two rows in the table can be identical Use Primary Key field(s) to uniquely identify one record from another Tables in relational database can be linked Using Foreign Key
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Chapter 6.2 - Developing Business Systems with Databases -...

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