What does before mean in mysql

The BEFORE clause in MySQL performs operations before triggering events, and is used to verify data, modify data, trigger event notifications, etc. The syntax is: CREATE TRIGGER trigger_name BEFORE event_type ON table_name FOR EACH ROW BEFORE [statements]. Example trigger to verify validity before inserting a record: IF NEW.salary < 10000 THEN SET NEW.salary = 10000; END IF;

# #BEFORE in MySQL

BEFORE is a keyword in MySQL that is used to specify the operation to be performed before the trigger is executed. A trigger is a special database object that is fired when a specific event occurs.

Purpose

The BEFORE clause is used to execute a specific SQL statement before the triggering event occurs. These statements can perform the following operations:

Verify the validity of the data
• Modify the data that will be inserted, updated, or deleted
• Record trigger events
• Send notification or message

Syntax

The BEFORE clause is used in the CREATE TRIGGER statement, the syntax is as follows:

<code>CREATE TRIGGER trigger_name
BEFORE event_type
ON table_name
FOR EACH ROW
BEFORE [statements]</code>

Where:

• trigger_name is the name of the trigger
• event_type is the trigger event type, such as INSERT, UPDATE or DELETE
• table_name is the table for which the trigger is to be created
• FOR EACH ROW Specifies that the trigger is fired on each row in the table
• [statements] is the SQL statement executed before the trigger event occurs.

Example

The following example creates a BEFORE trigger that verifies the validity of data before inserting a record into the table:

<code>CREATE TRIGGER validate_data
BEFORE INSERT
ON employees
FOR EACH ROW
BEFORE
  IF NEW.salary < 10000
  THEN
    SET NEW.salary = 10000;
  END IF;</code>

This trigger will be executed before new records are inserted into the employees table. It checks if the value of salary column is less than 10000. If so, it sets the value of the salary column to 10000 to ensure that the data in the table is always valid.

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