Kế toán doanh nghiệp - Chapter 4: Relational databases and enterprise systems

Chapter 4 Relational Databases and Enterprise SystemsCopyright © 2014 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.Learning ObjectivesLO#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 systems4-2Introduction of DatabaseA 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. A Network data model is a flexible model representing objects and their relationships. A Relational data model is a data model that stores information in the form of related two-dimensional tables.4-3LO# 1Introduction of DatabaseRelational data models are the dominant data model form in use today likely because they offer many advantages over other data models, including:Flexibility and ScalabilitySimplicityReduced Information Redundancy4-4LO# 1Definitions for DatabasesDatabase 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.4-5LO# 2Fundamentals of Relational DatabasesEntities 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. A foreign key in the relational database model serves as an attribute in one table that is a primary key in another table. A foreign key acts to provide a logical relationship, or a link, between two tables. 4-6LO# 2Fundamentals of Relational DatabasesThree Main ConstructsTable/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 are associated with one instance. 4-7LO# 2Fundamentals of Relational DatabasesBasic Requirements of TablesThe 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. 4-8LO# 2Fundamentals of Relational DatabasesBasic Requirements of TablesEach 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-to-many relationship. All other non-key attributes in a table must describe a characteristic of the class (table) identified by the primary key. 4-9LO# 2Microsoft Access to Implement a Relational DatabaseIntroduction 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. ----Forms are utilized by users to enter data into tables and view existing records. 4-10LO# 2Microsoft Access to Implement a Relational DatabaseReports 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. 4-11LO# 2Structured 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).4-12LO# 3Structured Query Language (SQL)4-13The 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 queryThe FROM clause to the SELECT statement indicates the name of table(s) from which to retrieve data. LO# 3Structured 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.4-14LO# 3Structured Query Language (SQL)4-15The 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.LO# 3Structured Query Language (SQLSix relational operators in SQLRelational Operators Meaning= equal!= or not equal greater than>= greater than or equal to4-16LO# 3Structured Query Language (SQLSQL 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.COUNT(X): gives the number of rows that satisfy the given condition.4-17LO# 3Enterprise SystemsEnterprise 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. 4-18In fact, for a popular ERP product (SAP/ERP) installation, there are 10,000 tables that are all linked to each other!LO# 4Enterprise SystemsES 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 supply chain and customer relationship management systems.4-19LO# 4Enterprise SystemsChallenges of Enterprise System Implementationintegrating 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, andgetting any big project implemented at a firm. 4-20LO# 4Enterprise SystemsEnterprise Systems Computing in a CloudIn 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 concern of cloud computing clients. 4-21LO# 5