---
title: "Explain the SQL triggers and their uses"  
description: "SQL triggers are powerful tools for enforcing rules, auditing changes, automating tasks, and maintaining data integrity within a database system."  
author: "Ashutosh Patel"  
published: 2024-07-08  
updated: 2024-07-08  
canonical: https://www.mindstick.com/articles/336344/explain-the-sql-triggers-and-their-uses  
category: "mssql server"  
tags: ["mssql server", "sql server", "sql"]  
reading_time: 4 minutes  

---

# Explain the SQL triggers and their uses

#### SQL Server Triggers

SQL triggers are procedural code that is **automatically executed** in response to certain events in a specific table or database view. These events can also be `INSERT`, `UPDATE`, `DELETE` operations, or specific data-modification conditions.

#### Create SQL Trigger

The SQL `CREATE TRIGGER` statement is used to create SQL Triggers and the `ALTER TRIGGER` is used to update the created SQL TRIGGERs

## Syntax-

```javascript
USE Database_Name
GO

CREATE TRIGGER trg_Name ON [table_Name]/[view_Name]
BEFORE/AFTER INSERT/UPDATE/DELETE
AS
BEGIN
-- SQL statement here
END
```

#### Uses of SQL Triggers

## Enforcing Business Rules

- Triggers can impose [complex business](https://www.mindstick.com/forum/161972/is-sql-more-vital-for-solving-complex-business-problems-or-power-bi-tableau-for-insights) rules and [data integrity](https://www.mindstick.com/forum/160197/what-is-the-normalization-in-sql-server-explain-its-impact-on-data-integrity-and-performance) constraints that cannot be enforced using built-in constraints (such as foreign key and check constraints) provided by the [database management](https://answers.mindstick.com/qa/115622/does-mindstick-software-training-include-database-management-and-cloud-computing) system (`DBMS`).
- For example, if certain conditions are not met, the trigger can inhibit an `INSERT` or `UPDATE` operation, [ensuring data](https://answers.mindstick.com/qa/113211/what-are-the-uses-of-blockchain-for-ensuring-data-integrity-in-ar-healthcare-applications) integrity.

## Auditing and Logging Changes

- Triggers are often used to track changes made to data in a database.
- They can log information about who made the change, what data was changed, when the change occurred, and provide a history of changes for compliance or troubleshooting.

**Automating [repetitive tasks](https://answers.mindstick.com/qa/102118/describe-the-role-of-software-in-automating-repetitive-tasks)**

- Triggers can enable operations whenever a data change occurs.
- For example, if an order is canceled, the trigger can automatically update the relevant tables or send notifications to the relevant parties.

## Maintaining Derived Data

- Triggers can automatically maintain derived data or summary information.
- For example, when a new invoice is entered, the trigger can update the total amount due to the customer based on all unpaid invoices.

## Complex Integrity Constraints

- Triggers can impose complex integrity constraints with [multiple tables](https://www.mindstick.com/forum/160909/how-to-join-multiple-tables-and-retrieve-specific-columns-in-sql-server) or conditions.
- This may include cross-table validation or ensuring that specific conditions are met before data manipulation is allowed.

#### Components of SQL Triggers

**Trigger Event** A specific event that fires a trigger, such as an INSERT, UPDATE, or DELETE.\
**Trigger Condition (Optional)** A condition that must be true for the trigger to work.\
**Trigger Action** The code or actions executed when the trigger fires. This can be an SQL statement or a call to a [stored procedure](https://www.mindstick.com/forum/12886/stored-procedure-error-transaction-count-mismatch).

## Example-

## Creating an SQL Triggers

Here is an SQL Trigger created that inserts that data automatically into `UserHistory`table when **deleted** from `Users` table,

```javascript
USE MyCollegeDb
GO

CREATE TRIGGER trg_UserHistory ON [Users]
AFTER DELETE
AS
BEGIN
SET NOCOUNT ON;

-- SQL query for insert deleted data from Users table into UserHistory table
INSERT INTO UserHistory(UserID, UserName, UserContact, Email, DateOfBirth, UpdateDate)
SELECT UserID, UserName, UserContact, Email, DateOfBirth, GETDATE() FROM [deleted]

SET NOCOUNT OFF
END
```

## In the example above-

`trg_UserHistory` is the name of the Trigger.

`AFTER DELETE` means that this trigger will automatically fire when any record/data will deleted from `Users` table

`SET NOCOUNT ON/OFF` is used to ignore the counting of affecting rows in the table by SQL statements.

> Note: you can aslo add multiple events in a trigger like- INSERT, UPDATE, DELETE

## Syntax-

```javascript
USE Database_Name
GO

CREATE TRIGGER trg_Name ON [table_Name]
AFTER INSERT, UPDATE, DELETE
AS
BEGIN
-- SQL statement here
END
```

## Where to See the Created Triggers

To see the created above trigger in the SQL Server [Management System](https://www.mindstick.com/blog/11871/making-progress-in-chemical-manufacturing-how-a-laboratory-information-management-system-lims-ens)(SSMS), follow the given steps,

**Open** and **Login** into SSMS -> Expant the **Database** folder from the **Object Explorer** in the left window -> Your Database Name folder (`MyCollegeDb`) -> Table name on which you created the trigger -> Expand the **Triggers** folder -> here your created trigger on this table will appear.

SQL triggers are powerful tools for enforcing rules, managing changes, automating operations, and maintaining data integrity in [database systems](https://answers.mindstick.com/qa/49683/who-is-e-f-codd-and-why-is-he-significant-in-the-development-of-modern-database-systems). They provide a way to extend DBMS functionality to meet specific application requirements that are not easily met by standard SQL implementations alone

**Also, Read:** [Define the PIVOT Table with examples in SQL server](https://www.mindstick.com/articles/336334/define-the-pivot-table-with-examples-in-sql-server)

---

Original Source: https://www.mindstick.com/articles/336344/explain-the-sql-triggers-and-their-uses

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