Question

I am using a Derby database.

I have a table like this:

TB_ORDERS
BUYER_NAME  DATE_CREATED    OTHER_COLLUMS ......
---------------------------------------------
 DAVID       2012-09-01         ----
 PETER       2012-09-14         ----
 DAVID       2012-09-05         ----
 PETER       2012-09-02         ----
 DAVID       2012-08-15         ----
 MARY        2012-09-02         ----
 MARY        2012-09-15         ----

I am trying to get a result grouped by BUYER_NAME where each group should be ordered by DATE_CREATED and finally everything ordered by the group’s most recent date, like this:

MARY    2012-09-15
MARY    2012-09-12
PETER   2012-09-14
PETER   2012-09-02
DAVID   2012-09-05
DAVID   2012-09-01
DAVID   2012-08-15

As you can see, the Mary’s Group has the most recent date_created so it is placed on top.
Then we get Peter’s group on second place (note that Peter’s group has a date “09-14” higher then one date on Mary’s group “09-12” however, Peter’s group is placed after Mary’s group as every thing should be ordered by the group’s most recent date.

I have tried every thing I know with no success. The closest I got was:

Select date_created, buyer_name 
From ORDERS 
Order By buyer_name,date_created Desc;

However, the groups are not ordered by the most recent group date.

Should I do that in my code or is there a better way?

Answer 1

This query will bring you the most recent date_created of each buyer_name, together with the result set that you already had. If you include this new column in your Order By clause it should do the trick:

Select o.date_created, o.buyer_name,
       (select max(date_created) from orders where buyer_name = o.buyer_name) as most_recent_date
From ORDERS o
Order By most_recent_date, o.buyer_name, o.date_created Desc