Want to eliminate duplicate record based on only column value

Question

http://sqlfiddle.com/#!9/ea4d2/1

Here is the SQLfiddle to look at. storepkid 16 is repeated 2 times. But I want it only one time. I tried DISTINCT but it eliminate entire duplicate row so it's not working in this case. What changes do I need to make in query to get proper result? Please help.

NOTE: forgot to mention in initial question that I tried GROUP BY too but it's giving incorrect data in record set result. I tried to use GROUP BY in following ways.

http://sqlfiddle.com/#!9/ea4d2/20

http://sqlfiddle.com/#!9/ea4d2/17

NOTE2: @Gabriel Valdez Timbol, I want result like this. Row with duplicate storepkid should be eliminated.

| Storepkid | selldate | 
+---------------+-----------------------+
|     19    |  August, 25 2015 10:00:00 | 
|     12    |  August, 24 2015 19:00:00 | 
|     16    |  August, 24 2015 16:00:00 | 
|     15    |  August, 23 2015 13:00:00 | 
|     17    |  August, 21 2015 10:00:00 | 

Answer 1

You can use max function. Use the below query

SELECT p.storepkid, max(p.selldate) AS recentselldate 
FROM 
(SELECT storepkid, purchasedatetime AS selldate 
        FROM t_product_purchase 
 UNION ALL 
 SELECT storepkid, starttime AS selldate 
        FROM t_service_purchase 
 UNION ALL 
 SELECT storepkid, selldatetime AS selldatetime 
       FROM t_coupon_purchase ) p 
GROUP BY storepkid
order by max(p.selldate)
DESC LIMIT 0,5

OUTPUT:

| Storepkid |        selldate           | 
+---------------------------------------+
|     19    |  August, 25 2015 10:00:00 | 
|     12    |  August, 24 2015 19:00:00 | 
|     16    |  August, 24 2015 16:00:00 | 
|     15    |  August, 23 2015 13:00:00 | 
|     14    |  August, 21 2015 13:15:00 | 

Check the DEMO HERE