绑定DropDownList去掉反复值

绑定DropDownList去掉重复值
从表中绑定某个字段,但有重复值,请问怎么去掉

------解决方案--------------------------------------------------------
试试把设为主键,
SELECT a.FreID, a.FreightWay
FROM freightLogAS a INNER JOIN
(SELECT MIN(FreID) AS id
FROM freightLog
GROUP BY FreightWay ) AS b ON a.FreID= b.FreID