Triggers Interview

Module 1: Introduction to Oracle Triggers

• 1.1. What is a Trigger?
• Definition of a trigger
• Purpose and importance of triggers in Oracle
• Trigger vs. Constraints
• 1.2. Types of Triggers
• DML Triggers (INSERT, UPDATE, DELETE)
• DDL Triggers (Data Definition Language)
• LOGON and LOGOFF Triggers
• INSTEAD OF Triggers
• Compound Triggers
• 1.3. Trigger Execution Order
• BEFORE vs. AFTER triggers
• Trigger firing sequence
• Statement-level vs. Row-level triggers

Module 2: Creating and Managing Triggers

• 2.1. Trigger Syntax
• Basic structure of a trigger
• CREATE TRIGGER statement
• Trigger body and triggering event
• 2.2. Trigger Components
• Trigger timing (BEFORE, AFTER)
• Trigger event (INSERT, UPDATE, DELETE)
• Trigger condition (WHEN clause)
• 2.3. Enabling and Disabling Triggers
• ENABLE/DISABLE commands for triggers
• ALTER TRIGGER
• Impacts on DML operations

Module 3: DML Triggers

• 3.1. BEFORE and AFTER INSERT Triggers
• Syntax and examples
• Use cases for BEFORE and AFTER INSERT triggers
• 3.2. BEFORE and AFTER UPDATE Triggers
• Syntax and examples
• Updating specific columns
• Using the :NEW and :OLD pseudo-records
• 3.3. BEFORE and AFTER DELETE Triggers
• Syntax and examples
• Handling cascading deletes
• Deleting related data from other tables
• 3.4. Conditional Trigger Firing
• Using the WHEN clause to conditionally fire a trigger
• Example use cases for conditional triggers
• 3.5. Row-Level vs. Statement-Level Triggers
• Understanding row-level triggers
• Statement-level triggers
• Performance implications

Module 4: Complex Triggers

• 4.1. Compound Triggers
• Definition and use of compound triggers
• Combining multiple actions in a single trigger
• Benefits and limitations of compound triggers
• 4.2. INSTEAD OF Triggers
• Usage of INSTEAD OF triggers
• Common scenarios where INSTEAD OF triggers are used (e.g., views)
• 4.3. Mutating Table Errors
• What causes mutating table errors?
• Solutions to avoid mutating table errors
• Handling mutating tables with compound triggers

Module 5: Advanced Trigger Concepts

• 5.1. Triggering on Views
• Triggering DML operations on views
• Using INSTEAD OF triggers on views
• 5.2. Triggering on Sequences
• Using triggers to capture sequence values
• Managing sequences in triggers
• 5.3. Database Triggers for Auditing
• Auditing with triggers (INSERT, UPDATE, DELETE)
• Tracking changes in audit tables
• Implementing custom audit trails
• 5.4. Complex Logic in Triggers
• Writing advanced logic for triggering events
• Conditional statements and loops inside triggers
• Managing exceptions in triggers

Module 6: Performance and Optimization

• 6.1. Trigger Performance Impact
• How triggers can affect performance
• Identifying slow-performing triggers
• Best practices for optimizing trigger performance
• 6.2. Trigger Best Practices
• Minimizing the complexity of triggers
• Reducing overhead on the database
• Using triggers with care in high-volume environments
• 6.3. Handling Multiple Triggers for the Same Event
• Firing sequence of multiple triggers for the same DML operation
• Managing dependencies between multiple triggers

Module 7: Error Handling and Exception Management

• 7.1. Exception Handling in Triggers
• Defining and raising exceptions in triggers
• Using EXCEPTION blocks for error handling
• 7.2. Managing Runtime Errors
• Handling errors that occur during trigger execution
• Reraising exceptions and logging errors
• 7.3. Logging and Debugging Triggers
• Writing logs to capture trigger execution
• Debugging trigger issues with DBMS_OUTPUT

Module 8: Trigger Security and Restrictions

• 8.1. Security Considerations with Triggers
• Ensuring the security of triggers
• Preventing unauthorized changes via triggers
• 8.2. Restrictions on Triggers
• Restrictions on the use of triggers
• Preventing infinite trigger loops
• 8.3. Managing Triggers Across Schemas
• Cross-schema trigger execution
• Handling permissions for triggers across schemas

Module 9: Working with DDL Triggers

• 9.1. What are DDL Triggers?
• Purpose and examples of DDL triggers
• Triggering on CREATE, ALTER, and DROP operations
• 9.2. Creating and Managing DDL Triggers
• Syntax for DDL triggers
• Using AUDIT_TRAIL and DDL_EVENT system variables
• 9.3. Auditing DDL Operations
• Using DDL triggers to track schema changes
• Capturing DDL changes in audit tables
• Implementing system-level security via DDL triggers

Module 10: Triggers for Logon and Logoff Events

• 10.1. LOGON and LOGOFF Triggers
• Purpose and examples
• Triggering events on user logins and logoffs
• Security uses (logging, user activity tracking)
• 10.2. Managing Sessions Using Triggers
• Managing session-level information via triggers
• Session expiration triggers

Module 11: Trigger Management and Best Practices

• 11.1. Monitoring Trigger Activity
• Querying trigger activity in Oracle
• Identifying trigger usage and performance bottlenecks
• 11.2. Dropping and Altering Triggers
• Using DROP TRIGGER and ALTER TRIGGER
• Considerations when modifying triggers
• 11.3. Best Practices for Writing Triggers
• Writing efficient and maintainable triggers
• Keeping triggers modular and clear
• Using triggers as a last resort for business logic

Module 12: Summary and Advanced Topics

• 12.1. Summary of Key Concepts
• Recap of DML, DDL, and compound triggers
• Best practices for trigger design and performance
• 12.2. Advanced Trigger Topics
• Triggers and replication in Oracle
• Triggers for distributed databases
• Managing triggers in cloud-based Oracle environments
• 12.3. Next Steps in Oracle Advanced Topics
• Advanced performance tuning techniques
• Exploring Oracle's Advanced Security Features