Re: Create a foreign key from a field that is part of a mulitple primary key

"naud" <naudjf_at_yahoo.fr> wrote in message news:1e1a7efc.0409020717.48e48228_at_posting.google.com...
| Hi,
|
| i had a table named T_A, with a double primary key : (A,B)
|
| Then i created a table named T_B with a field : C.
|
| I want this field T_B.C to take only values that already exist in
| field T_A.A.
|
| So i tried to create a foreign key on my field T_B.C, pointing on the
| field T_A.A : an error message appeared "not possible to create a
| foreign key on a field that is not a primary key".
|
| How can i solve this....? If U have any idea, please mail me !!
|
| THANX very much.

whenever you have a multi-part primary key, as in T_A(A,B), you have either a dependent table or an intersection table -- that implies that part of the PK is actually an FK to another table.

so in your case, column A looks like it should be an FK to the PK of another table 'T_X' (which appears to be missing)

once that table (T_X) is created with the appropriate PK (and TA(A) is declared as an FK to it) then you can create an FK on T_B(C) referencing the correctly modelled PK of table 'T_X'

++ mcs Received on Thu Sep 02 2004 - 10:27:43 CDT