An assertion is a predicate expressing a condition we wish database to always satisfy. The correct syntax for Assertion is :

Explanation

CREATE ASSERTION <assertion name> CHECK <predicate> is the proper syntax. For example, an assertion demanding that there is no more than one president among the employees: CREATE ASSERTION AT_MOST_ONE_PRESIDENT CHECK ((SELECT COUNT(*) FROM EMP e WHERE e.job = 'PRESIDENT') <= 1).