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Jul 17, 2024 · Trigger is a statement that a system executes automatically when there is any modification to the database. In a trigger, we first specify when the trigger is to be executed and then the action to be performed when the trigger executes.
- Introduction to SQL Triggers
- Trigger Creation Statement Syntax
- Row Level Trigger vs. Statement Level Trigger
- SQL Trigger Usages
- SQL Trigger Example
- Modify Triggers
- Delete Triggers
- GeneratedCaptionsTabForHeroSec
A trigger is a piece of code executed automatically in response to a specific event occurred on a table in the database. A trigger is always associated with a particular table. If the table is deleted, all the associated triggers are also deleted automatically. A trigger is invoked either before or after the following event: 1. INSERT– when a new r...
To create a trigger, you use the following statement: Let’s examine the syntax in more detail: 1. First, specify the name of the trigger after the CREATE TRIGGERclause. 2. Next, use either BEFORE or AFTER keyword to determine when to the trigger should occur in response to a specific event e.g., INSERT, UPDATE, or DELETE. 3. Then, specify the name ...
There are two types of triggers: row and statement level triggers. A row level trigger executes each time a row is affected by an UPDATE statement. If the UPDATE statement affects 10 rows, the row level trigger would execute 10 times, each time per row. If the UPDATEstatement does not affect any row, the row level trigger is not executed at all. Di...
You typically use the triggers in the following scenarios: 1. Log table modifications. Some tables have sensitive data such as customer email, employee salary, etc., that you want to log all the changes. In this case, you can create the UPDATEtrigger to insert the changes into a separate table. 2. Enforce complex integrity of data. In this scenario...
We will use the employees table in the sample databasefor the demonstration. Suppose we want to log the changes of values in the salary column. To do this, we create a separate tablefor storing the changes and use a trigger to insert the changes into this table. The following statement creates the salary_changestable. The salary_changes table logs ...
To change the trigger definition, you use the CREATE OR REPLACE TRIGGERstatement. Basically, the CREATE OR REPLACE TRIGGERcreates a new trigger if it does not exist and changes the trigger if it does exist. The CREATE OR REPLACE TRIGGER statement is similar to the CREATE TRIGGERstatement as follows:
To delete a trigger, you use the DROP TRIGGERstatement as follows: The IF EXISTS option allows you to delete a trigger if the trigger exists. If the trigger does not exist, then the statement does nothing. However, if you don’t have the IF EXISTSoption, the database system may issue an error if you try to drop a non-existing trigger. Again, if you ...
Learn how to create and use SQL triggers to execute code automatically in response to table events. See how to log table modifications, enforce data integrity, and modify triggers with examples.
Dec 29, 2022 · Learn how to create triggers for DML, DDL, or logon events in SQL Server or Azure SQL Database. See the syntax, arguments, and examples of CREATE TRIGGER statement.
Mar 17, 2022 · Learn how to create and use SQL Server triggers for data modification and auditing. See the syntax, types, options and scenarios of triggers with examples and code.
- Daniel Farina
Aug 15, 2024 · Learn how to use SQL triggers to automate tasks, maintain data integrity, and enhance database performance. See examples of creating, modifying, deleting, and displaying triggers in MySQL and Oracle.
Learn how to create and use SQL triggers, special stored procedures that execute in response to database events. See the syntax and an example of a trigger that logs changes to a table in SQL Server.
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Learn how to use the CREATE TRIGGER statement to create a new trigger that fires automatically when an event such as INSERT, UPDATE, or DELETE occurs against a table. See syntax, examples, and virtual tables for triggers: INSERTED and DELETED.
