SQL constraint (Is this allowed)?!

Question

Dear all,
I'm designing a database at the moment. I have a table called Student. In this table I have the following fields:
Student ID, Name, Grant ID*, Fund ID*
The Grant ID* and Fund ID* are foreign keys referencing a grant table and a fund table.
In a normal situation, the student has a grant OR typical fund such as self funding or scholarship etc.
the question is : can I have a constraint to force the table entry to one column only but not the other and vise versa.So the student will only have a grant OR typical fund?
I don't know the name of this constraint, I have searched for a long time but without knowing what I am searching for Its like searching for a needle in a hay stack.

Answer 1

Something like this perhaps
SCOTT @ jcave102 Local> ed
Wrote file afiedt.buf
  1  create table a (
  2    col1 number,
  3    col2 number,
  4    constraint chk_a1 check( (col1 is not null and col2 is null) or
  5                             (col2 is not null and col1 is null))
  6* )
SCOTT @ jcave102 Local> /
Table created.
Elapsed: 00:00:00.01
SCOTT @ jcave102 Local> insert into a values( 1, null );
1 row created.
Elapsed: 00:00:00.01
SCOTT @ jcave102 Local> insert into a values( null, 1 );
1 row created.
Elapsed: 00:00:00.01
SCOTT @ jcave102 Local> insert into a values( 1, 1 );
insert into a values( 1, 1 )
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CHK_A1) violated
Elapsed: 00:00:00.07
SCOTT @ jcave102 Local> insert into a values( null, null );
insert into a values( null, null )
ERROR at line 1:
ORA-02290: check constraint (SCOTT.CHK_A1) violated
Elapsed: 00:00:00.01Justin