Q:

Check constraint with condition

I'm wondering if this condition can be done by a check constraint or do I need to create a trigger.
Condition : if student admited date is not null then exam mark is null
Remark: Constaint case OR Trigger 
What I tried :
ALTER TABLE ADMITED_TABLE
ADD CONSTRAINT AAAA CHECK
 ( CASE  WHEN  DATEADMITED IS NOT NULL THEN MARK NULL END);

Error:
ORA-00920: invalid relational operator
00920. 00000 -  "invalid relational operator"

A:

A check constraints takes a boolean condition, so you'd have to frame this logic in a form of such a condition:
ALTER TABLE ADMITED_TABLE
ADD CONSTRAINT AAAA CHECK
(dateadmited IS NULL OR mark IS NULL);

