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📘 Day 101: Triggers

Welcome to Day 101! Today, we'll learn about Triggers, which are special stored procedures that are automatically executed when certain events occur in the database.

What is a Trigger?

A trigger is a database object that is associated with a table and that activates when a particular event (e.g., an INSERT, UPDATE, or DELETE) occurs for the table.

Key Points

  • Triggers are used to maintain the integrity of the data in a database.
  • Triggers can be executed before or after an INSERT, UPDATE, or DELETE operation.
  • The BEFORE triggers are used to validate the data before it is saved to the database.
  • The AFTER triggers are used to perform some action after the data has been saved to the database.

Creating and Managing Triggers

CREATE TRIGGER

The CREATE TRIGGER statement is used to create a new trigger.

CREATE TRIGGER trigger_name
{BEFORE | AFTER} {INSERT | UPDATE | DELETE}
ON table_name
[FOR EACH ROW]
BEGIN
    -- trigger body
    -- this is where you put your SQL statements
END;

Note: The syntax for creating triggers can vary between different SQL databases. SQLite supports triggers.

💻 Exercises: Day 101

Please see the exercises.sql file for today's exercises.

Previous: Day 100 – Day 100: Stored Procedures • Next: Day 102 – Day 102: Common Table Expressions (CTEs)

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