CHECT Constraint

• Defines a condition that each row must satisfy
  
• The following expressions are not allowed:
  - References to CURRVAL, NEXTVAL, LEVEL, and ROWNUM pseudocolumns
  - Call to SYSDATE, UID, USER, and USERENV functions
  - Queries that refer to other values in other rows
  

..., salary	NUMBER(2)

     CONSTRAINT	emp_salary_min

		CHECK (salary > 0),...