Which constraint enforces value rules such as minimum, maximum, or a specified set of values?

Which constraint enforces value rules such as minimum, maximum, or a specified set of values?

• A. Unique Constraint
• B. Check Constraint
• C. Not Null Constraint
• D. Primary Key Constraint

Answer: (B)

A check constraint enforces value rules by evaluating a condition on the data in a column for every row. This is how you express minimum or maximum limits or membership in a specific set, such as CHECK (age >= 0 AND age <= 120) or CHECK (status IN ('active','inactive','pending')). When a row is inserted or updated, the database checks that the condition is true; if not, the operation is rejected. By contrast, a unique constraint ensures all values in a column are distinct, a not null constraint requires a value to be present (not NULL), and a primary key constraint combines uniqueness with not null to identify each row.

A check constraint enforces value rules by evaluating a condition on the data in a column for every row. This is how you express minimum or maximum limits or membership in a specific set, such as CHECK (age >= 0 AND age <= 120) or CHECK (status IN ('active','inactive','pending')). When a row is inserted or updated, the database checks that the condition is true; if not, the operation is rejected. By contrast, a unique constraint ensures all values in a column are distinct, a not null constraint requires a value to be present (not NULL), and a primary key constraint combines uniqueness with not null to identify each row.