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：

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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