SQL Fundamentals · question
Q.03 of 41
What is a Primary Key and what are its characteristics?
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- Uniqueness: No duplicate values allowed
- Not NULL: Cannot contain NULL values
- Immutable: Values should not change once assigned
- One per table: Each table can have only one primary key
- Automatic indexing: Database automatically creates an index on primary key
CREATE TABLE employees (
emp_id INT PRIMARY KEY,
name VARCHAR(100) NOT NULL
);
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