mysql不知道是不是关键字 of

今天写sq中 给表起个别名是 of 然后怎么就是不行，一直在报错，也没有提示是关键字，换成其他的别名就可以，后来在of上加个反引号就行了。就是键盘数字“1”左边的按键

SELECT
	ofg.goods_id,
	of.order_id,
	of.last_total_amount,
	of.o_pay_time,
	of.order_status,
	of.order_pay_status
FROM
	mall_cloud_order.order_form  `of`
	LEFT JOIN  mall_cloud_order.order_form_goods ofg ON ofg.of_id = of.id 
WHERE
	of.order_pay_status = 2 
	AND order_status IN ( 20, 27, 30, 40, 50 ) 
	AND of.pay_way IN ( 1, 2 )