数据库基础知识培训胶片.ppt

* Practice 1 Overview This is the first of many practices. The solutions (if you require them) can be found in Appendix A. Practices are intended to introduce all topics covered in the lesson. Questions 2–4 are paper-based. In any practice, there may be “if you have time” or “if you want an extra challenge” questions. Do these only if you have completed all other questions within the allocated time and would like a further challenge to your skills. Perform the practices slowly and precisely. You can experiment with saving and running command files. If you have any questions at any time, attract the instructor’s attention. Paper-Based Questions For questions 2–4, circle either True or False. Instructor Note Let the students know that to get a listing of the tables they can access during the course, the command is: SELECT * FROM TAB; Schedule: Timing Topic 55 minutes Lecture 30 minutes Practice 85 minutes Total * Lesson Aim Functions make the basic query block more powerful and are used to manipulate data values. This is the first of two lessons that explore functions. It focuses on single-row character, number, and date functions, as well as those functions that convert data from one type to another, for example, character data to numeric data. * SQL Functions Functions are a very powerful feature of SQL and can be used to do the following: Perform calculations on data Modify individual data items Manipulate output for groups of rows Format dates and numbers for display Convert column data types SQL functions sometimes take arguments and always return a value. Note: Most of the functions described in this lesson are specific to Oracle’s version of SQL. Instructor Note This lesson does not discuss all functions in great detail. It presents the most common functions with a brief explanation of them. * Character Functions Single-row character functions accept character data as input and can return both character and numeric values. Charac