SQL Triggers - Deep level discussion

What you'll learn

Strong Foundation – Learn the basics of triggers, including AFTER and INSTEAD OF triggers, with step-by-step examples.

Advanced Concepts – Explore multi-row/bulk insert handling, nested triggers, and error handling inside triggers.

Real-world Use Cases – Understand how triggers enforce business rules, maintain audit logs, and automate tasks.

Hands-on Practice – Work on practical examples like handling duplicates, cascading updates, and validating inserted data.

Requirements

If you have seen previous Part6 - You are good to go.

Description

What are Triggers in SQL Server?Learn the fundamental concept of triggers—special stored procedures that run automatically in response to INSERT, UPDATE, or DELETE events on a table or view.Types of Triggers in SQL ServerUnderstand the difference between AFTER triggers (also known as FOR triggers), INSTEAD OF triggers, and DDL triggers, and where each is best used.AFTER Triggers ExplainedThese triggers run after the triggering event has been completed. Perfect for audit logging and enforcing referential integrity.INSTEAD OF Triggers ExplainedLearn how to replace the standard insert, update, or delete action with custom logic. Very useful for views and scenarios where we want to modify or reject the incoming data.Creating a Trigger from ScratchStep-by-step walkthrough of writing a trigger using CREATE TRIGGER, binding it to a table, and defining the execution logic using T-SQL.Understanding INSERTED and DELETED TablesExplore how SQL Server internally creates two logical tables during trigger execution:INSERTED for new dataDELETED for old dataThese are key for comparing old vs new values.Row-level vs Statement-level LogicLearn how triggers process multiple rows at once, and why using cursors or set-based logic is crucial in writing efficient triggers.Trigger to Prevent Duplicate DataCreate a trigger that checks for duplicate entries (like customer email or username) and prevents insertion or modifies it dynamically.Trigger for Data Correction Before InsertUse INSTEAD OF INSERT to clean or modify data—like trimming strings, changing case, or assigning default values—before the data goes into the table.Creating Audit Trail Using TriggersAutomatically log who, what, and when into an audit table for all INSERT, UPDATE, and DELETE actions—without changing your application code.Capturing User Name and TimestampUse SYSTEM_USER, GETDATE(), and other functions inside a trigger to record the user and time of change.Complex Business Rule EnforcementWrite triggers to apply business rules—such as preventing deletion of a customer if they have pending orders, or limiting price discounts.Triggers on ViewsLearn how to use INSTEAD OF triggers to allow insert/update/delete actions on views that would otherwise be read-only.Nested Triggers in SQL ServerUnderstand what happens when one trigger causes another trigger to fire. Learn how to enable or disable nested triggers at the server level.Recursive Triggers – Risks and ControlLearn how a trigger can call itself (directly or indirectly) and how to prevent unwanted recursive loops using RECURSIVE_TRIGGERS setting.Trigger with TRY.CATCH Error HandlingUse TRY.CATCH blocks inside triggers to catch and log errors without breaking the entire transaction.Disabling and Enabling TriggersUse DISABLE TRIGGER and ENABLE TRIGGER commands to control when triggers should execute, without needing to drop them.Dropping a Trigger SafelyLearn how to remove a trigger using DROP TRIGGER, and understand the best practices to avoid accidental data issues.Trigger Performance TipsUnderstand how triggers can slow down transactions if not optimized. Learn techniques like avoiding cursors, using SET NOCOUNT ON, and indexing.Avoiding Common MistakesCommon pitfalls include using scalar logic in multi-row triggers, assuming triggers fire in a specific order, or failing to handle NULL values properly.Triggers vs Constraints vs Stored ProceduresCompare and contrast these tools. Learn when to use a trigger, when a constraint is better, and when stored procedures should handle logic instead.Using Triggers for Email Alerts (Advanced)Use a trigger to call a stored procedure that sends an email when certain critical conditions are met (e.g., stock falls below threshold).DDL Triggers (Schema Change Tracking)Go beyond DML triggers. Learn about DDL Triggers that fire on CREATE, ALTER, DROP statements—useful for security and monitoring.Trigger Metadata and System ViewsQuery system tables like sys.triggers, sys.trigger_events, and sys.sql_modules to view all trigger definitions and properties.

Overview

Section 1: Introduction

Lecture 1 Introduction to After Trigger

Lecture 2 Insert After Trigger

Lecture 3 Delete After Trigger

Lecture 4 Instead of Trigger Intro

Lecture 5 Project on Instead of INSERT

Lecture 6 More conditions in Project

Lecture 7 Discard Negative Quantity

Lecture 8 AFTER Update Trigger

This course is for SQL developers who want to learn every thing about TRIGGERS