Hi,
Could some one please explain the importance of foreign key?
I have learnt that foreign key is a key from dependent table which is derived from a primary key of the parent table and most importantly foreign key allows duplicates.
For ex: If a parent table EMPLOYEE has a primary key EMPNO
EMPNO
30
60
and Dependent table PRJ has a foreign key RESPEMP
RESPEMP
30
30
now if I want to update the empno - 30 of the parent table EMPLOYEE as 80
But since the value 30 already occurred in the dependent table PRJ it is not allowing me to update the value in Parent table EMPLOYEE. how could I resolve this?
and at the same time I cant delete the same empno 30 from the parent table EMPLOYEE, since the value 30 occurred in the dependent table PRJ.
How could I resolve this.
Thanks for your help in advance.
Necessity of FOREIGN KEY
Moderators: Kalicharan, Moderator Group
Necessity of FOREIGN KEY
Last edited by Aashiq on Thu Mar 29, 2012 10:25 pm, edited 1 time in total.
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