Trigger is a rule that constitutes a set of T-SQL statements activated in response to a certain actions such as insert or delete. Trigger are used to ensure data integrity before or after performing data manipulation.

BEFORE UPDATE Trigger

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Description

A BEFORE UPDATE Trigger means that MySQL will fire this trigger before the UPDATE operation is executed.

Syntax

The syntax to create a BEFORE UPDATE Trigger in MySQL is:

Parameters or Arguments

OR REPLACE: It is an optional parameter. It is used to re-create the trigger if it already exists. It facilitates you to change the trigger definition without using a DROP TRIGGER statement.

trigger_name : name of the trigger to create.

BEFORE UPDATE: indicates that the trigger will fire before the UPDATE operation is executed.

table_name: name of the table that the trigger is created on.

Restrictions

  • You can not create a BEFORE trigger on a view.
  • You can update the NEW values.
  • You can not update the OLD values.

Example

Let’s look at an example of how to create an BEFORE UPDATE trigger using the CREATE TRIGGER statement in MySQL.

If you had a table created as follows:

We could then use the CREATE TRIGGER statement to create an BEFORE UPDATE trigger as follows:

 

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Rasmi Ranjan

A tech guy who loves to learn code. I'm open source enthusiast and a delicious coffee maker

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