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What is trigger in Oracle?- Triggers are constructs in PL/SQL that need to be just created and associated with a table.
- Once they are created, the table associated with it gets updated due to an UPDATE, INSERT or a DELETE, the triggers get implicitly fired depending upon the instructions passed to them.
- In many cases, triggers supplement the standard capabilities of Oracle to provide a highly customized database management system.
- For example, a trigger can permit DML operations against a table only if they are issued during regular business hours.
- The standard security features of Oracle, roles and privileges, govern which users can submit DML statements against the table.
- In addition, the trigger further restricts DML operations to occur only at certain times during weekdays.
- This is just one way that you can use triggers to customize information management in an Oracle database.
In addition, triggers are commonly used to:
1. Automatically generate derived column values
2. Prevent invalid transactions
3. Enforce complex security authorizations
4. Enforce referential integrity across nodes in a distributed database
5. Enforce complex business rules
6. Provide transparent event logging
7. Provide sophisticated auditing
8. Maintain synchronous table replicates
9. Gather statistics on table access
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