利用Oracle触发器类型实现逻辑功能（oracle触发器类型）

With the development of computer technology, more and more people use the database to manage their data. Database triggers are powerful tools for manipulating data in databases. As a powerful tool in database programming, Oracle triggers are widely used. Triggers are used to implement logic functions, enforce business rules and enhance data integrity.

Oracle triggers contain two main types: row-level triggers processed against each row affected by the statement, and statement-level triggers handled once for the entire statement. The row-level triggers are divided into: BEFORE triggers, which are executed before data is changed, and AFTER triggers, which are executed after data is changed. Statement-level triggers are mainly divided into: BEFORE and AFTER triggers, which are executed both before and after data changes.

①For example, to implement the logic function of calculating the cumulative score after each row is inserted into the table, the BEFORE Row trigger can be used. The code is as follows:

CREATE OR REPLACE TRIGGER score_update

BEFORE INSERT

ON user_score

FOR EACH ROW

BEGIN

:NEW.total := :old.total + :must.score;

END;

②For example, to ensure that the user’s mail is not blank after modifying, the AFTER Row trigger can be used. The code is as follows:

CREATE OR REPLACE TRIGGER mail_check

AFTER UPDATE

ON user_info

FOR EACH ROW

BEGIN

IF :new.mail IS NULL THEN

RAISE_APPLICATION_ERROR(-20001, ‘Mail cannot be empty!’);

END IF;

END;

The Oracle trigger is a very powerful tool for database programming. It can not only implement logic functions, enforce business rules and enhance data integrity, but also simplify the code maintenance and make the database more robust. The programming of triggers is also relatively simple, so many database developers are using triggers to achieve a variety of data manipulation functions.