💡 SQL Interview Question: 👉 How do you add a PRIMARY KEY constraint to an existing table in SQL? This is a frequently asked SQL interview question to test your understanding of constraints and table modification. Here’s the clean SQL query 👇 ALTER TABLE employees ADD CONSTRAINT pk_employees PRIMARY KEY (employee_id); 🎯 Explanation: ALTER TABLE is used to modify an existing table ADD CONSTRAINT defines a new table constraint pk_employees is the name of the primary key constraint employee_id b

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