Hi And Best Regards To Everyone(Problem In Updating Table)

intimate2talent · **Posted:** Mon Apr 16, 2007 4:05 am

Greetings!

Could anyone solve my follwing problem.

Act i m trying to update the table(month) for the query "update month(tablename) set name='Jeny' where monthid=2;" by using follwing Hibernate Code:-

Month m=new Month();
session.get(Month.class,m.getMonthid());

m.setMonthid(2);

/*It takes '2' as a condition for column monthid here i dont know why? If i change it to any value which is not there in table month for column monthid like '4444' then it will not update the table.*/
m.setName("Jeny");

session.update(m);

Now before The code table is like
--------------------------------------------
monthid Name
-------------------------------------------
2 John
------------------------------------------

After executing the above hibernate code the table will get updated like
--------------------------------------------
monthid Name
-------------------------------------------
2 Jeny
------------------------------------------

===============================================

Now my question is that if i want to run follwing query with the same way of hibernate code what i have used above then how should i do it?
The query is:-- "update month(tablename) set monthid=44,name="abc" where monthid=2 and name="Jeny";" [/b]

Hope i have put my question properly.If Anybody can help me out as much as soon then i will be so greatful to him.

Thanks Lot

With Regards
Saurav Jain

piet.t · **Joined:** Fri May 12, 2006 4:05 am **Posts:** 106

Hi,

without your mappings it is hard to say for sure, but I assume monthid is the id-property of your Month-class?

Then there's quite a few queer things about your code....
1.) If you want to get() a certain row and you know its id-attribute you should use

Code:

Month m = session.get(Month.class,2);

to really get the object representing your id-value.
2.) DON'T change the id-attribute of a persistent instance. That is really, really bad. For hibernate different id-values means differente instances. That's why the row doesn't get updated when you change the monthid to a value that isn't in the DB (hibernate will look for a row containing that value and try to update that row).
3.) If you want to update the primary-key-values of any of your tables you should rethink your database-design. primary-keys are for unique identification of any given entity and you wouldn't want to have any entity's identity changed (this is bad style even in pure relational programming). If you need a new Row with monthid = 44 and name="abc" then insert it:

Code:

Month m2 = new Month();
m2.setMonthid(44);
m2.setName("abc);
session.save(m2);

If you no longer need the row with monthid=2 then delete it:

Code:

Month m = session.get(Month.class,2);
session.delete(m);

Regards

piet

chucky · **Joined:** Mon Jun 12, 2006 5:33 am **Posts:** 63

Hi intimate2talent,

when loading your month object into memory (session.get(Month.class,m.getMonthid());), you're getting a java OBJECT with a specified id (e.g. hashcode). During a hibernate session, hibernate synchronizes your java OBJECT with your database ROW. So your object is mapped and BOUND to that row. You cannot just change the id as you would do in a SQL Statement. So you must insert a new row with the id 4444 and delete the one with id 2.
Hope that helps

chucky.

Don't forget to rate
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Month m=new Month();
session.get(Month.class,m.getMonthid());

m.setMonthid(2);

/*It takes '2' as a condition for column monthid here i dont know why? If i change it to any value which is not there in table month for column monthid like '4444' then it will not update the table.*/
m.setName("Jeny");

session.update(m);