40. Primary key

DBMS Published 30 Sept 2026 Updated 30 Sept 2026 0 Views Verified

Define a primary key and show a MySQL implementation.

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Answer & Explanation

4 Answers

Verified

Option A

CREATE TABLE customers (id TEXT UNIQUE, name VARCHAR(100));

Additional Explanation

This option is incorrect for the stated requirement.

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Option B

CREATE TABLE customers (id BIGINT, name VARCHAR(100));

Additional Explanation

This option is incorrect for the stated requirement.

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Option C

CREATE TABLE customers (id BIGINT INDEX, name VARCHAR(100));

Additional Explanation

This option is incorrect for the stated requirement.

Verified Correct Answer

Option D

CREATE TABLE customers (id BIGINT PRIMARY KEY, name VARCHAR(100));

Additional Explanation

Correct implementation. Prefer parameterized queries in application code, validate affected rows for UPDATE/DELETE, and use transactions for related writes.