返回类型

IF判断

CASE status
		WHEN 3 THEN '微信'
		WHEN 2 THEN '支付宝'
		ELSE '其他'
END AS status_chinese,

返回时间格式

FROM_UNIXTIME(create_time, '%Y-%m-%d %H:%i:%s') AS create_time

Join

LEFT JOIN

SELECT t.user, o.order
FROM tableA 
LEFT JOIN order as o t.user.user_id = o.order.user_id