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Stored Procedures Interview Questions

What Interviewers Are Testing

Stored procedure interview questions evaluate your understanding of database-side business logic, parameterized SQL execution, and the trade-offs of server-side programming.

Interview Questions & Model Answers

Q1

What is a stored procedure and how is it different from a function?

A

A stored procedure is a precompiled group of SQL statements stored in the database that can be called by name. A function always returns a value and can be used in a SELECT statement. A procedure may or may not return values (via OUT parameters), cannot be used in SELECT, and can perform data manipulation. Procedures are called with CALL or EXEC; functions with SELECT or WHERE.

Example
-- Stored Procedure
CREATE PROCEDURE get_orders(IN cust_id INT)
BEGIN
  SELECT * FROM orders WHERE customer_id = cust_id;
END;
CALL get_orders(42);

-- Function
CREATE FUNCTION get_discount(price DECIMAL) RETURNS DECIMAL
BEGIN
  RETURN price * 0.9;
END;
SELECT get_discount(100.00);
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Potential Follow-up Questions:

  • Can stored procedures have transactions inside them?
Q2

What are the advantages and disadvantages of stored procedures?

A

Advantages: reduced network traffic (one call instead of multiple round-trips), precompiled execution plans (faster), security layer (grant EXECUTE permission instead of direct table access), code reuse, centralized business logic. Disadvantages: hard to test and debug, logic spread between application and database is harder to maintain, version control is harder, vendor lock-in (PL/SQL vs T-SQL vs PL/pgSQL differ), difficult to scale horizontally.

Potential Follow-up Questions:

  • When would you choose to use stored procedures in a modern microservices architecture?

Frequently Asked Questions

What is a stored procedure in SQL?
A stored procedure is a named, precompiled set of SQL statements stored in the database server. It can accept input parameters (IN), output parameters (OUT), and perform queries, data manipulation, and control flow logic. Called with CALL proc_name(params) in MySQL/PostgreSQL or EXEC proc_name params in SQL Server.
What is the difference between a stored procedure and a trigger?
A stored procedure is called explicitly by an application or another procedure. A trigger fires automatically in response to an INSERT, UPDATE, or DELETE event on a specific table. Triggers cannot be called directly; stored procedures must be called explicitly. Both run server-side SQL code.

Related Interview Topics

TransactionsIndexingDatabase NormalizationSql Joins

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