4 Relational Databases（课件）- 《会计信息系统英文版》同步教学（人民大学版）

Chapter 4 Relational Databases 4-1 Learning Objectives Explain the importance and advantages of databases. Describe the difference between database systems and file-based legacy systems. Explain the difference between logical and physical views of a database. Explain fundamental concepts of database systems such as DBMS, schemas, the data dictionary, and DBMS languages. Describe what a relational database is and how it organizes data. Create a set of well-structured tables to store data in a relational database. Perform simple queries using the Microsoft Access database. 4-2 Data Hierarchy Field Attributes about an entity Record Related group of fields File Related group of records Database Related group of files 4-3 Advantages of Database Systems Data Integration Files are logically combined and made accessible to various systems. Data Sharing With data in one place it is more easily accessed by authorized users. Minimizing Data Redundancy and Data Inconsistency Eliminates the same data being stored in multiple files, thus reducing inconsistency in multiple versions of the same data. Data Independence Data is separate from the programs that access it. Changes can be made to the data without necessitating a change in the programs and vice versa. Cross-Functional Analysis Relationships between data from various organizational departments can be more easily combined. 4-4 Database Terminology Database Management System (DBMS) Interface between software applications and the data in files. Database Administrator (DBA) Person responsible for maintaining the database Data Dictionary Information about the structure of the database Field names, descriptions, uses 4-5 Logical vs. Physical Physical View Depends on explicitly knowing: How is the data actually arranged in a file Where is the data stored on the computer Logical View A Schema separates storage of data from use of the data Unnecessary to explicitly know how and where data is stored. 4-6 Schemas Describe the logic