MySQL 5.7

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CREATE TABLE IF NOT EXISTS `ORDER` (
  `Order No.` INT UNSIGNED NOT NULL COMMENT 'The order of the inspected equipment',
  `Order_Type` CHAR(8) NOT NULL COMMENT 'External or Internal work',
  `Engine_Description` VARCHAR(45) NOT NULL COMMENT 'Description of the Engine',
  `Equipment_Quantity` INT UNSIGNED NOT NULL COMMENT ' Number of the inspected equipment',
  `Required_Task` VARCHAR(8) NOT NULL COMMENT 'Whether Repair or Overhaul',
  PRIMARY KEY (`Order No.`))
ENGINE = InnoDB
COMMENT = '\n';
CREATE TRIGGER before_orders_insert
BEFORE INSERT
ON `ORDER` FOR EACH ROW
BEGIN
 IF NEW.Order_Type  ='External' THEN
     SET new.`Engine_Description` = '';
 END IF;

END;
CREATE TRIGGER before_orders_UPDATE
BEFORE UPDATE
ON `ORDER` FOR EACH ROW
BEGIN
 IF NEW.Order_Type  ='External' THEN
     SET new.`Engine_Description` = '';
 END IF;

END;
INSERT INTO `ORDER` VALUES (1,'External','test descrition',1,'Repair')
,(2,'Internal','test descrition',2,'Repair')
SELECT * FROM `ORDER`


Order No.
Order_Type
Engine_Description
Equipment_Quantity
Required_Task


1
External

1
Repair

2
Internal
test descrition
2
Repair