This is the DBMS questions and answers section on "Constraints" with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. To include integrity constraint in a existing relation use :
- A. Create table
- B. Modify table
- C. Alter table
Answer: Option C
Explanation:
Alter table
SYNTAX – alter table table-name add constraint , where constraint can be any constraint on the relation.
2. Which of the following is not a integrity constraint ?
- A. Not null
- B. Positive
- C. Unique
- D. Check ‘predicate’
Answer: Option B
Explanation:
Positive
Positive is a value and not a constraint.
3. Foreign key is the one in which the ________ of one relation is referenced in another relation.
- A. Foreign key
- B. Primary key
- C. References
- D. Check constraint
Answer: Option B
Explanation:
Primary key
The foreign-key declaration specifies that for each course tuple, the department name specified in the tuple must exist in the department relation.
4. Domain constraints, functional dependency and referential integrity are special forms of _________.
- A. Foreign key
- B. Primary key
- C. Assertion
- D. Referential constraint
Answer: Option C
Explanation:
Assertion
An assertion is a predicate expressing a condition we wish the database to always satisfy.
5. Which of the following is the right syntax for assertion?
- A. Create assertion 'assertion-name' check 'predicate';
- B. Create assertion check 'predicate' 'assertion-name';
- C. Create assertions 'predicates';
- D. All of the mentioned
Answer: Option A
Explanation:
Create assertion 'assertion-name' check 'predicate';
