数据库某字段会存在重复值，要找出表里所有不重复的数据

1、先根据这个字段，使用count查询重复数据的重复个数

2、筛选count值是1的数据

例如：

SELECT
	* 
FROM
	(
	SELECT
		order_number AS number,
		count( order_number ) AS count 
	FROM
		( SELECT order_number FROM xx_orders WHERE use_status = 2 AND order_type != 4 ) AS ordery 
	WHERE
		order_number LIKE 'XD%' 
	GROUP BY
		order_number 
	) AS ordert 
WHERE
	ordert.count = 1