Database Management Supplement 1

2 I. The Hierarchy of Data Database File (Entity, Table) Record (info for a specific entity, Row) Field (Attribute, Column) Data Types (only one type for a field)

3 II. Relational Database Relational Database Model: Most popular database model. Data are stored in multiple tables. One table can be related to another table if they have a common field (usually primary key and foreign key). Primary key: one field or a combination of fields (column in a table) that uniquely identifies each record (row in a table). If there is no one single field that can be used to uniquely identify a record, a primary key is made of more than one field and called composite (concatenated) keys.

4 What are Tasks for Database Administrator? Define data characteristics Establish standards Coordinate users and designers Create, test and document programs Data backup and recovery Security controls

5 What are standards important? Databases and tables were developed at different points in time by different people Consistent user interfaces Standard reports Data definition Document changes in programs and databases.

6 III. Microsoft Access 1. Basic definitions Application generators: It enables you to create applications without writing any programs. For Access database applications, you can create tables, queries, reports, forms, even macros without writing any programming commands. Seven objects of Access database: table, query, report, form, macro, VB module, and page.

7 Table: stores data for an entity (e.g., customer, order, loan, etc.) in rows (records) and columns (fields). A record includes all information about an instance of an entity. A field is a piece of information in a record. Query: answers questions by retrieving certain fields of certain records from one or more tables that satisfy a set of criteria.

8 Form: A form provides a user-friendly interface to enter, maintain and view records, and it is based on a table or a query. Report: It presents data from tables or queries in the way that you want. Page: It is a Web interface supported by Access and stored as a separate HTML file. Macro: a set of Access macro commands that automates tasks. Module: a program written in Visual Basic to automate tasks.

9 2. Design a query QBE (Query By Example) vs. SQL: QBE is part of application generator. It enables you to generate queries without writing any programming commands – SQL is a query language for programming. – QBE is easier to use. SQL is more flexible and powerful. Managers may prefer to use QBE.

10 To design a query, you need to answer four questions: – What output do you want to see? (fields to show and how to sort) – What tables are involved? – What constraints are given? (criteria and specified by developer or user) – How are the tables joined together? (directly or through other tables)

11 Query Exercise:

12 IV. Database Design What are goals for database design? 1.Capability of storing all pertinent data 2.Reduce redundant data 3.Keep the number of tables to a minimum 4.Normalize the tables so that to minimize update and deletion problems

13 V. Database Design What is normalization? Normalization is a design process that minimizes redundant data by separating data into interrelated tables. The normalization process can be defined by seven categories called normal forms in the order from the least restrictive to the most restrictive: Unnormal form, First normal form, Second normal form, Third normal form, Boyce-Codd normal form, Fourth normal form, and Fifth normal form.