Answer & Explanation

4 Answers
Verified

Option A

ALTER TABLE customers ADD INDEX email UNIQUE FALSE;
Additional Explanation
This option is incorrect for the stated requirement.
Sarkari Resultess
Editorial Answer 1
Verified

Option B

ALTER TABLE customers ADD CHECK email UNIQUE;
Additional Explanation
This option is incorrect for the stated requirement.
Sarkari Resultess
Editorial Answer 2
Verified

Option C

ALTER TABLE customers SET email PRIMARY;
Additional Explanation
This option is incorrect for the stated requirement.
Sarkari Resultess
Editorial Answer 3
Verified Correct Answer

Option D

ALTER TABLE customers ADD CONSTRAINT uq_customers_email UNIQUE (email);
Additional Explanation
Correct implementation. Prefer parameterized queries in application code, validate affected rows for UPDATE/DELETE, and use transactions for related writes.
Sarkari Resultess
Editorial Answer 4