摘要：
Lesson Thirty-one Success storyYesterday afternoon Frank Hawkins was telling me about his experience as a young man.Before he retired, Frank was the head of a very large business company,But as a boy he used to work in a small shop. It was his job to repair bicycles andAt that time he used to work f 阅读全文
摘要：
触发器是存放在数据库中的一种特殊类型的子程序。它不能被用户程序直接调用，而是当特定事件或操作发生时由系统自动调用执行。触发器主要用于对数据库特定操作、特定事件的监控和响应。这些特定的事件或操作包括启动数据库、登录数据库、关闭数据库等系统事件、执行DML和DDL等操作。一、概念1.触发器的分类（1）DML触发器，依据于基本表或简单视图建立的触发器；（2）instead of触发器，依据于复杂视图建立的触发器；（3）系统事件触发器，依据系统事件或DDL操作建立的触发器。2.触发器的简介触发器是存放在数据库中的一种特殊类型的子程序。有PL/SQL块构成的触发器，只能包含select、insert、u 阅读全文