Which SQL statement correctly alters table STUDENT to add a named CHECK constraint GradeCheck requiring that Grade values be greater than 0 (strictly positive)?

Question

Solve this multiple-choice question and choose the correct option.

Curioustab · Accepted Answer

Introduction / Context:CHECK constraints enforce row-level data rules directly in the database. Adding a named constraint improves maintainability and allows targeted enable/disable and error messages. The task is to identify the correct SQL syntax for adding such a constraint. Given Data / Assumptions: Table name: STUDENT. Constraint name: GradeCheck. Rule: Grade must be greater than 0. Concept / Approach: Most SQL dialects support the pattern: ALTER TABLE CHECK (). The predicate uses normal boolean logic; here it is Grade > 0. The verb “ALTER CONSTRAINT” is typically used to modify properties of an existing constraint, not to define the check expression from scratch. Step-by-Step Solution: 1) Choose ALTER TABLE to modify structure and constraints of an existing table.2) Use ADD CONSTRAINT to create a new, named constraint.3) Specify CHECK (Grade > 0) as the rule. Verification / Alternative check: Run a small test: insert a row with Grade = 0 or Grade = -1 and confirm the database rejects it with a constraint violation; insert Grade = 1 and confirm success. Why Other Options Are Wrong: Option A: ALTER CONSTRAINT requires an existing constraint; syntax omits CHECK keyword. Option B: Missing the CHECK keyword; incomplete definition. Option D: Incorrect because Option C is valid. Common Pitfalls: Forgetting to name the constraint, which complicates later maintenance; writing Grade >= 0 by mistake if the business rule requires strictly positive values. Final Answer: ALTER TABLE STUDENT ADD CONSTRAINT GradeCheck CHECK (Grade > 0); ADD CONSTRAINT

Which SQL statement correctly alters table STUDENT to add a named CHECK constraint GradeCheck requiring that Grade values be greater than 0 (strictly positive)?

Answer

Explanation