how to add trigger in mysql code example

Example 1: trigger in mysql syntax

CREATE TRIGGER trigger_name
{BEFORE | AFTER} {INSERT | UPDATE| DELETE }
ON table_name FOR EACH ROW
trigger_body;

Example 2: mysql trigger example

-- The following statement creates an AFTER UPDATE trigger on the sales table:

DELIMITER $$

CREATE TRIGGER after_sales_update
AFTER UPDATE
ON sales FOR EACH ROW
BEGIN
    IF OLD.quantity <> new.quantity THEN
        INSERT INTO SalesChanges(salesId,beforeQuantity, afterQuantity)
        VALUES(old.id, old.quantity, new.quantity);
    END IF;
END$$

DELIMITER ;

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