如何在SQL中更新每个组的最大行

Question

I just added the 'default' column to my DB. I am trying to set the default value to '1' based on the latest 'addDate' per accountId.

+----+-----------+--------------------+--------+
| id | accountId |      addDate       | default|
+----+-----------+--------------------+--------+
| 1  | 45        |2012-02-29 08:41:59 |        |
| 2  | 55        |2012-03-29 08:41:59 |        |
| 3  | 45        |2012-04-29 08:41:59 |        |
| 4  | 55        |2012-05-29 08:41:59 |        |
| 5  | 60        |2012-05-29 08:41:59 |        |
+----+-----------+--------------------+--------+

I found I was able to isolate the proper rows by using =>

select * from tble1 
where addDate = (select max(addDate) from tble1 as sl where sl.accountId = tble1.accountId);

I need to be able to run an UPDATE that sets 'default' column to '1' only 1 time per 'accountId' basing it off of latest 'addDate'.

Answer 1

try this

 UPdate Table1 
 SET `default` = 1 
 where addDate in (select * from (
                               select max(addDate) from table1 as sl group by accountId)t
                                 )

DEMO HERE

Answer 2

UPDATE table1 x
  LEFT
  JOIN table1 y
    ON y.accountid = x.accountid
   AND y.adddate > x.adddate
   SET x.default = 1
 WHERE y.id IS NULL;

or (faster)

UPDATE table1 x
 JOIN 
    ( SELECT accountid  
           , MAX(addDate) max_adddate 
        FROM table1 
       GROUP 
          BY accountid
    ) y
   ON y.accountId = x.accountId
  AND y.max_adddate = x.adddate
  SET x.default = 1;