How to write trigger in oracle database
Oracle triggers are database objects that automatically perform actions when a specific event occurs in a table, such as inserting, updating, or deleting a record. To create a trigger, use the syntax CREATE TRIGGER
ON FOR
ASBEGIN END;. Triggers can insert, update, or delete records in another table, call procedures or functions, and execute user-defined code.
Oracle Database Trigger Creation Guide
What is an Oracle trigger?
Oracle trigger is a database object that automatically performs a series of actions when a specific event occurs in a table, such as inserting, updating, or deleting a record. Triggers can be used to validate data, perform calculations, or record audit events, etc.
How to create a trigger
To create an Oracle trigger, use the following syntax:
CREATE TRIGGER <触发器名称> ON <表名称> FOR <事件> AS BEGIN -- 执行触发的动作 END;Copy after loginTrigger event
The following events can be defined for triggers:
- INSERT: Triggered when a new record is inserted
- UPDATE: at
- DELETE triggered when an existing record is updated: Triggered when an existing record is deleted
Trigger action
The trigger can perform the following operations:
- Insert: Insert a new record into another table
- Update: Update another Existing records in one table
- Delete:Delete records from another table
- Call a procedure or function:Execute user-defined code
Trigger Example
For example, the following trigger stores employee names into the "AuditLog" table when a new record is inserted into the "Employees" table :
CREATE TRIGGER audit_employee_insert ON Employees FOR INSERT AS BEGIN INSERT INTO AuditLog (action, table_name, record_id, employee_name) VALUES ('INSERT', 'Employees', NEW.employee_id, NEW.employee_name); END;Copy after loginNote:
- Trigger names must be unique.
- Triggers can contain multiple actions.
- Triggers can be disabled during DDL (Data Definition Language) operations such as creating or dropping tables.
- Triggers can be created as many times as needed.
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