Changing foreign key results in new row

i´m currently working on my first Java application based on a MySQL DB. I´m using EclipseLink2.0 and NetBeans, at the time i am facing a behaviour i cannot explain, maybe someone has stumbled over this problem in the past and can help me with this. Here goes:

Table 1 has the PK of table 2 as Fk. Application-side, there is an UI where users can genera开发者_如何学编程te content for table 1. The value for the fk(Table2ID) is beeing chosen with a dropdown menu, which gets each values by reading the Collection of table2 rows. Now, when i try to change the value for the fk to another (already existing) value, instead of doing just that, a new row with a fresh ID is generated on table2, all other column values are cloned from the row i tried to change the Fk to. So, for example, when i try to set table1 rows 3,4 and 5 to table1.fkcolumn =6 (i.e Table2ID=6), the program instead clones the row with ID=6 3 times and sets each of the table1 columns to one of them.

Any help would be greatly appreciated .

The problem is you are changing the primary key of an entity. In EclipseLink, when you change the PK of an entity, you have a new entity. As such, Eclipselink inserts the new rows and leaves the old rows alone.

To get around this you have three choices: 1) Change the database. Primary keys really shouldn't be changed. 2) Set the application to execute an update query which changes the primary key values and requery them. 3) Delete the old rows and re-create with a new primary key.