需要两个选择吗？

SELECT  CASE WHEN a.FromID = 'yourIDHere' 
                THEN c.Name
                ELSE b.Name
        END Name,
        CASE WHEN a.FromID = 'yourIDHere' 
                THEN c.Age
                ELSE b.Age
        END Age,
        a.VisitTime,
        CASE WHEN a.FromID = 'yourIDHere' 
                THEN 'You'
                ELSE 'Friend'
        END DirectionOfVisit
FROM    Visit a
        INNER JOIN UserProfile b
            ON a.FromID = b.Uid
        INNER JOIN UserProfile c
            ON a.ToID = c.Uid
WHERE   'yourIDHere' IN (a.FromID, a.ToID)
ORDER   BY a.VisitTime

简要说明:

查询将显示您访问过的朋友或访问过您的朋友的姓名,并显示访问的方向.显示时You,表示您已访问过您朋友的个人资料,否则会显示Friend该朋友是否已访问过您.

SQLFiddle演示