Lecture Accounting information systems: Chapter 4 - Richardson, Chang, Smith

Chapter 4 - Relational databases and enterprise systems. In this chapter students will be able to: Describe the advantages of relational databases, explain basic relational database principles, describe how to query using Structured Query Language (SQL), understand the purpose and basic framework for an enterprise system, assess how cloud computing facilitates enterprise systems.

Chapter Relational Databases and Enterprise Systems Copyright © 2014 McGraw­Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw­Hill Education Learning Objectives • LO#1 Describe the advantages of relational databases • LO#2 Explain basic relational database principles • • • LO#3 Describe how to query using Structured Query Language (SQL) LO#4 Understand the purpose and basic framework for an enterprise system LO#5 Assess how cloud computing facilitates enterprise systems 4-2 LO# Introduction of Database • A database is a collection of related data for various uses Three types of data models: • A Hierarchical data model organizes data into a tree-like structure that allows repeating information using defined parent/child relationships 4-3 LO# Introduction of Database • Relational data models are the dominant data model form in use today likely because they offer many advantages over other data models, including: § Flexibility and Scalability § Simplicity § Reduced Information Redundancy 4-4 LO# Definitions for Databases • • • Database Management System (DBMS) – The DBMS is defined as a computer program that creates, modifies and queries the database Specifically, the DBMS is designed to manage a database’s storage and retrieval of information Data Dictionary – The data dictionary describes the data fields in each database record such as field description, field length, field type (e.g., alphanumeric, numeric), etc Database Administrator – The person responsible for the design, implementation, repair and security of a firm’s database 4-5 LO# Fundamentals of Relational Databases • • • • • • Entities and Attributes: A class in the relational database model could be a person, place, thing, transaction, or event about which information is stored Classes could be grouped into resources (R), events (E), and agents (A) in data modeling Attributes are characteristics, properties, or adjectives that describe each class Keys and Relationships: A primary key is an attribute or combination of attributes that uniquely identify a specific row in a table 4-6 serves as A foreign key in the relational database model LO# Fundamentals of Relational Databases • • • • Three Main Constructs Table/Relation: The primary construct, used for data storage with rows and columns much like a spreadsheet Each table in a database represents either a class or a relationship between classes Tables need to be properly linked to make a relational database Column: The columns in a table are called fields that represent the attributes or characteristics of the class or relationship Rows: The rows in a table are called records or tuples The records represent all the specific data values that 4-7 are associated with one instance LO# Fundamentals of Relational Databases • • • Basic Requirements of Tables The Entity Integrity Rule: the primary key of a table must have data values (cannot be null) The Referential Integrity Rule: the data value for a foreign key must either be null or match one of the data values that already exist in the corresponding table 4-8 LO# Fundamentals of Relational Databases • • • • • Basic Requirements of Tables Each attribute in a table must have a unique name Values of a specific attribute must be of the same type Each attribute (column) of a record (row) must be single-valued This requirement forces us to create a relationship table for each many-tomany relationship All other non-key attributes in a table4-9 must LO# Microsoft Access to Implement a Relational Database • Introduction to Microsoft Access Access is a simple database management system that can be used to run databases for individuals and small firms The Access system is composed of seven objects that are used to implement relational databases Tables are used to store data which consists of a series of rows (records) and columns (attributes) connected by relationships (links between tables) Queries are a tool used to retrieve and display data derived from records stored within the database 4-10 LO# Microsoft Access to Implement a Relational Database • • • • Reports are used to integrate data from one or more queries and tables to provide useful information to decision makers Pages, Web-based forms, allow data to be entered into the database in real time from outside of the database system Macros are defined by users to automate processes like opening a specific form Access’s code can be altered by the use of modules 4-11 LO# Structured Query Language (SQL) • • • SQL (usually pronounced "Sequel") stands for Structured Query Language and is a computer language designed to query data in a relational database SQL is based on relational algebra and allows a user to query and update the database In a database, while queries allow the user to access, read and report on desired data, the responsibility of actually making physical changes to the relational database belongs to the Database Management System (DBMS) 4-12 LO# Structured Query Language (SQL) • • • The SELECT statement is used to begin a query The SELECT statement tells the query which columns (or attributes) of a table should be included in the query The FROM clause to the SELECT statement indicates the name of table(s) from which to retrieve data 4-13 LO# Structured Query Language (SQL) • • • The WHERE clause states the criteria that must be met to be shown in the query result The GROUP BY operator is used with aggregate functions on the query results based on one or more columns The ORDER BY clause identifies which columns are used to sort the resulting data If there is no ORDER BY clause, the order of rows returned by an SQL query will not be defined 4-14 LO# Structured Query Language (SQL) • • • • • • The INSERT INTO operator inserts data into a SQL table The UPDATE operator is for updating data in a SQL table The DELETE FROM operator deletes data from a SQL table SELECT DISTINCT clause selects a column without showing repetitive values The BETWEEN operator can be used to specify the end points of a range Membership Operator (IN) allows you to test whether a data value matches the specified target values 4-15 LO# Structured Query Language (SQL Six relational operators in SQL Relational Operators Meaning • = • != or • < less than • greater than >= to greater than or equal • equal not equal 4-16 LO# Structured Query Language (SQL SQL language provides several convenient aggregate functions to be used in SQL commands These aggregate functions include AVG, SUM, MAX, MIN, and COUNT Their definitions are as follows: • • AVG(X): gives the average of column X SUM(X): gives the summation of all rows that satisfy the selection criteria for column X • MAX(X): gives the maximum value of column X • MIN(X): gives the minimum value of column X 4-17 LO# Enterprise Systems Enterprise systems (ES), also known as Enterprise Resource Planning (ERP) systems, are commercialized information systems that integrate and automate business processes across a firm’s value chain located within and across organizations Typically, an enterprise system uses relational data model as a basis for the information system The use of primary and foreign keys links the hundreds of tables that form the basis for the enterprise system In fact, for a popular ERP product (SAP/ERP) installation, there are 10,000 tables that are all linked to each other! 4-18 LO# Enterprise Systems • • • • ES accommodates the integration and support of the various business processes and information needs of a company ES has a higher level of internal transparency compared to the typically isolated legacy systems The purported informational benefits of an enterprise system include enhanced completeness, transparency, and timeliness of information needed to manage effectively an organization’s business activities The enterprise system serves as the backbone of the company’s internal business processes and serves as a connection with the external business processes for 4-19 LO# Enterprise Systems Challenges of Enterprise System Implementation • • • • • integrating various modules within the enterprise system, integrating with external systems such as the information system of a supplier and/or customer, integrating with the firm’s own existing legacy systems, converting data from existing legacy systems to the enterprise system, and getting any big project implemented at a firm 4-20 LO# Enterprise Systems Enterprise Systems Computing in a Cloud • • • • In recent years, cloud computing has emerged as a potential alternative to host enterprise systems and other firm computing needs Cloud computing is Internet-based computing where shared resources, software, and information are provided to firms on demand Cloud Computing can easily host enterprise system applications Cloud computing, of course, has disadvantages as well Ensuring that any sensitive data is secure and backed up frequently by the host is often a 4-21 concern of ... record (row) must be single-valued This requirement forces us to create a relationship table for each many-tomany relationship All other non-key attributes in a table 4-9 must LO# Microsoft Access... other data models, including: § Flexibility and Scalability § Simplicity § Reduced Information Redundancy 4- 4 LO# Definitions for Databases • • • Database Management System (DBMS) – The DBMS... Hierarchical data model organizes data into a tree-like structure that allows repeating information using defined parent/child relationships 4- 3 LO# Introduction of Database • Relational data