What is trigger in Oracle with example?
Table of Contents
What is trigger in Oracle with example?
A trigger is either a stored PL/SQL block or a PL/SQL, C, or Java procedure associated with a table, view, schema, or the database itself. Oracle Database automatically executes a trigger when a specified event takes place, which may be in the form of a system event or a DML statement being issued against the table.
How do Oracle triggers work?
Oracle Forms triggers are part of an Oracle Forms application and are fired only when a specific trigger point is executed within a specific Oracle Forms application. SQL statements within an Oracle Forms application, as with any database application, can implicitly cause the firing of any associated database trigger.
What is trigger and types of trigger?
A trigger defines a set of actions that are performed in response to an insert, update, or delete operation on a specified table. When such an SQL operation is executed, the trigger is said to have been activated. Triggers are optional and are defined using the CREATE TRIGGER statement.
Why triggers are written?
Triggers are written to be executed in response to any of the following events. A database manipulation (DML) statement (DELETE, INSERT, or UPDATE). A database definition (DDL) statement (CREATE, ALTER, or DROP). A database operation (SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN).
What are the usage of triggers?
Triggers allow you to perform the following tasks: Enforce business rules. Validate input data. Generate a unique value for a newly inserted row on a different file (surrogate function)
What are different events in triggers?
CORRECT ANSWER : Insert, Update, Delete. Discussion Board. Triggers.
How trigger is executed?
Following are the steps of trigger execution:
- Load the original record or initialize on insert.
- Override the old record values with the new values.
- Execute all before triggers.
- Run the system & user-defined validation rules.
- Save the record but do not commit the record to the database.
- Execute all after triggers.
Can we use rollback in trigger?
Changes made within triggers should thus be committed or rolled back as part of the transaction in which they execute. For this reason, triggers are NOT allowed to execute COMMIT or ROLLBACK statements (with the exception of autonomous triggers).
Can we write DDL in trigger?
We cannot natively execute DDL in any form of PL/SQL. including triggers. To do that we need to use dynamic SQL. Triggers have an additional wrinkle: they are fired as part of the transaction, and they have a limitation that forbids us from issuing a commit inside their body.
Can a trigger return a value?
Trigger functions invoked by per-row triggers can return a table row (a value of type HeapTuple ) to the calling executor, if they choose. A row-level trigger fired before an operation has the following choices: It can return NULL to skip the operation for the current row.
What is the advantage of trigger?
Advantages of Triggers in SQL 2. Allows us to reuse the queries once written. 3. Provides a method to check the data integrity of the database.
