Oracle database is currently the most widely used relational database management system in the world. It has rich functions and flexible configuration. In Oracle database, tables are an important part of data storage. The structure of the table includes column names, column types, constraints, etc. Modifying the table structure is a common data operation, but the modification operation may have a certain impact on the integrity and security of the data. Therefore, special attention needs to be paid when modifying the table structure.
In order to record the modification process of the table structure and ensure the integrity and traceability of the data, Oracle database provides a variety of methods to record table modifications. This article will introduce the following methods of modifying the record table.
Flashback Table was launched in the Oracle10g version, and it requires SYSTEM permissions to execute. Before executing Flashback Table, you can use the following statement to query which tables have logging enabled in the database:
SELECT LOG_MODE FROM V$DATABASE;
If the query result is "ARCHIVELOG", it means that the database has logging enabled.
When using Flashback Table, you need to pay attention to the following points:
The following is an example of a Trigger that records the modification history of the student table:
CREATE TABLE STUDENT_HISTORY ( ID INT PRIMARY KEY, OPERATION_TYPE VARCHAR(10) NOT NULL, OPERATE_TIME DATE NOT NULL, NAME VARCHAR2(50) NOT NULL, AGE INT NOT NULL, SEX VARCHAR2(10) NOT NULL, GRADE VARCHAR2(20) NOT NULL, REMARKS VARCHAR2(100) ); CREATE OR REPLACE TRIGGER STUDENT_HISTORY_TRG BEFORE DELETE OR UPDATE OR INSERT ON STUDENT FOR EACH ROW BEGIN IF DELETING THEN INSERT INTO STUDENT_HISTORY (ID, OPERATION_TYPE, OPERATE_TIME, NAME, AGE, SEX, GRADE, REMARKS) VALUES (:OLD.ID, 'DELETE', SYSDATE, :OLD.NAME, :OLD.AGE, :OLD.SEX, :OLD.GRADE, :OLD.REMARKS); ELSIF UPDATING THEN INSERT INTO STUDENT_HISTORY (ID, OPERATION_TYPE, OPERATE_TIME, NAME, AGE, SEX, GRADE, REMARKS) VALUES (:OLD.ID, 'UPDATE', SYSDATE, :NEW.NAME, :NEW.AGE, :NEW.SEX, :NEW.GRADE, :NEW.REMARKS); ELSIF INSERTING THEN INSERT INTO STUDENT_HISTORY (ID, OPERATION_TYPE, OPERATE_TIME, NAME, AGE, SEX, GRADE, REMARKS) VALUES (:NEW.ID, 'INSERT', SYSDATE, :NEW.NAME, :NEW.AGE, :NEW.SEX, :NEW.GRADE, :NEW.REMARKS); END IF; END;
This Trigger records the modification history of the student table into the STUDENT_HISTORY table. When performing insert, update, and delete operations, Trigger will record the operation type, operation time, student name, age, gender, grade, and remarks.
The advantages of using Trigger to record modification history are:
However, there are also some disadvantages to using Trigger:
The following is an AUDIT policy that records the user's insert, update, and delete operations on the EMPLOYEES table:
AUDIT INSERT, UPDATE, DELETE ON EMPLOYEES BY SESSION;
This statement will record the user's insert, update, and delete operations on the EMPLOYEES table. BY SESSION means recording the operation performed by which session. You can use the following statement to check the enabled status of Audit:
SELECT * FROM DBA_OBJ_AUDIT_OPTS WHERE OWNER='HR' AND OBJ_NAME='EMPLOYEES';
The advantage of using AUDIT to record table modification history is:
However, AUDIT also has some limitations:
Database Change Management Pack allows users to have a complete picture of the database change status, including:
In the Database Change Management Pack, users can specify the objects and policy options that need to be audited and generate change tracking data. It can also automatically generate change documentation and artifacts and conduct audits after each database change.
The advantages of using Database Change Management Pack are:
However, Database Change Management Pack also has some disadvantages:
Summary:
Oracle is currently the most widely used database in the world. It provides a variety of methods for recording table modification history, including Flashback Table, Trigger, AUDIT and Database Change Management Pack. Each of these methods has advantages and disadvantages, and users need to choose and use them according to specific circumstances.
When modifying the table structure, you must be extremely careful to avoid affecting the integrity and security of the data. If important data is saved in the database, it is recommended to back up the data before modifying it. Timely recording of table modification history and conducting audits are very effective in ensuring data integrity and security.
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