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 Post subject: SQL to UPDATE conditionally based on the MAX of a column
PostPosted: Mon Aug 28, 2017 2:43 am 
Newbie

Joined: Mon Aug 28, 2017 2:40 am
Posts: 1
I want to update column c5 (to 1) of each grouped date base on column c1,c2,c3 where c3 is maximum in same c1,c2 group.I am working with hql on oracle db

Code:
c1     |  c2 | c3 | c4 | c5 | c5 after update
2000  |   a | 01 | x  | 0  | 0
2000  |   a | 01 | y  | 0  | 0
2000  |   a | 01 | z  | 0  | 0
2000  |   a | 02 | z  | 0  | 1
2000  |   a | 02 | x  | 0  | 1
...........................
2000  |   b | 01 | x  | 0  | 0
2000  |   b | 01 | y  | 0  | 0
2000  |   b | 01 | z  | 0  | 0
2000  |   b | 02 | z  | 0  | 1
..........................
..........................
2001  |   a | 01 | x  | 0  | 0
2001  |   a | 01 | y  | 0  | 0
2001  |   a | 01 | z  | 0  | 0
2001  |   a | 02 | z  | 0  | 0
2001  |   a | 02 | x  | 0  | 0
2001  |   a | 02 | y  | 0  | 0
2001  |   a | 02 | w | 0  | 0
2001  |   a | 03 | y  | 0  | 1
2001  |   a | 03 | w  | 0  | 1
...........................
2001  |   b | 01 | x  | 0  | 0
2001  |   b | 01 | y  | 0  | 0
2001  |   b | 02 | x  | 0  | 1
2001  |   b | 02 | z  | 0  | 1


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 Post subject: Re: update conditionally base on maximum of a column
PostPosted: Tue Sep 05, 2017 1:45 am 
Hibernate Team
Hibernate Team

Joined: Thu Sep 11, 2014 2:50 am
Posts: 1638
Location: Romania
Easy peasy!

As long as you also have an id in your entries table, this is the SQL query you need to run:

Code:
int updateCount = entityManager.createNativeQuery(
   "update entries set c5 = 1 " +
   "where id in " +
   "( " +
   "    select id " +
   "    from ( " +
   "        select *, MAX (c3) OVER (PARTITION BY c1, c2) as max_c3 " +
   "        from entries " +
   "    ) t " +
   "    where t.c3 = t.max_c3 " +
   ") ")
.executeUpdate();


If the database does not support Windows Functions, then the query looks like this:

Code:
int updateCount = entityManager.createNativeQuery(
   "update entries set c5 = 1 " +
   "where id in " +
   "( " +
   "    select e.id " +
   "    from entries e  " +
   "    inner join ( " +
   "        select c1, c2, max(c3) as max_c3 " +
   "        from entries " +
   "        group by c1, c2 " +
   "    ) t " +
   "    on e.c1 = t.c1 and e.c2 = t.c2 and e.c3 = t.max_c3  " +
   ") " )
.executeUpdate();


Check out this article for more details.

_________________
If you liked my answer, you are going to love my High-Performance Java Persistence book and my blog as well.


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