tailieunhanh - Lecture Enterprise information systems: A pattern-based approach (3/e): Chapter 7 - Cheryl Dunn, J. Owen Cherrington, Anita Hollander

Chapter 7 - Information retrieval from relational databases. The objective of this chapter is to illustrate the means by which information can be retrieved (via querying) from relational databases to meet demands for enterprise decisions. | Chapter 7 Information Retrieval from Relational Databases Chapter Learning Objectives Identify and explain the purpose of the three primary relational algebra operators Identify and explain the primary components of a Structured Query Language (SQL) statement Identify the relational algebra operations achieved by a given SQL statement Create a SQL statement to retrieve requested information from a relational database Examine a SQL statement and the tables to which it will be applied and identify the query result Find errors in a SQL statement Create a Microsoft Query-by-Example (QBE) to retrieve information from relational tables Examine a Microsoft Access QBE query and the tables to which it applies and identify the query result Find errors in a Microsoft Access QBE query 7- Examples of Needs for Multiple Views of One Data Set Cash-basis versus Accrual Accounting Weighted Average versus FIFO or LIFO Double-Declining Balance Depreciation versus Straight Line Foreign Currency Translation How do we get these multiple views??????? 7- Answer: Query the Data Set What is Querying? It is asking questions about the data in the database and manipulating or combining the data in different ways We can isolate certain rows in tables, we can isolate certain columns in tables, we can join tables together, we can create calculations based on various data items, etc. 7- Querying/Information Retrieval Several ingredients are necessary for effective querying A database that is well-designed If tables are not fully relational or incompletely specified, or if conceptual model has not been correctly converted into relational form, querying will be difficult or impossible A query developer who understands the table structures and the nature of the data in the tables A query developer who understands the desired query output A query developer who has good logic and reasoning skills A query developer who knows the querying language used to retrieve information from the . | Chapter 7 Information Retrieval from Relational Databases Chapter Learning Objectives Identify and explain the purpose of the three primary relational algebra operators Identify and explain the primary components of a Structured Query Language (SQL) statement Identify the relational algebra operations achieved by a given SQL statement Create a SQL statement to retrieve requested information from a relational database Examine a SQL statement and the tables to which it will be applied and identify the query result Find errors in a SQL statement Create a Microsoft Query-by-Example (QBE) to retrieve information from relational tables Examine a Microsoft Access QBE query and the tables to which it applies and identify the query result Find errors in a Microsoft Access QBE query 7- Examples of Needs for Multiple Views of One Data Set Cash-basis versus Accrual Accounting Weighted Average versus FIFO or LIFO Double-Declining Balance Depreciation versus Straight Line Foreign Currency .