从两个数据库中删除重复的记录

我设法从两个不同的数据库中识别重复的记录:

select * from 
    taskperformance a,  taskperformance@dm_prod b
where 
    a.activityin = b.activityin
    and a.completiondate = b.completiondate

如何删除重复记录 b ?

我试过:

delete taskperformance@dm_prod  where exist ( 
select * from 
    taskperformance a,  taskperformance@dm_prod b
where 
    a.activityin = b.activityin
    and a.completiondate = b.completiondate ) 

但它删除的内容比我需要的要多。