Selecting customers that follow a particular trend

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Selecting customers that follow a particular trend

Author

Topic

velvettiger
Posting Yak Master

115 Posts

Posted - 2008-07-09 : 17:56:25

Hi,

Problem

In the below table:


donor    receptor  
1    ->     4
2    ->     5
4    ->     6

The above reads as follows...

Student 1 donates all of his/her money to Student 4
Student 2 donates all of his/her money to Student 5
Student 4 donates all of his/her money to Student 6

I would like to pull all of the ultimate donors from the above table. An ultimate donor is someone who is at all times a receptor and never a donor.

So in the above scenario Students 5 and 6 are ultimate donors. Does anyone have any ideas on how this can be accomplished?

I will be very appreciative of any inputs.

Thanks

singularity
Posting Yak Master

153 Posts

Posted - 2008-07-09 : 19:13:43

select distinct receptor
from yourtable a
left join (select donor from yourtable) b on a.receptor = b.donor
where b.donor is null