Why should I use stored procedures?

Stored procedures offer benefits such as reusability, performance improvements, and centralized security for SQL logic.

How to Write Stored Procedures in SQL | FullStackPrep.Dev

Q: What is a stored procedure in SQL?

A stored procedure is a reusable block of SQL code stored in the database that performs a specific task or set of tasks.

💡 Concept Name

Stored Procedures are reusable SQL routines stored in the database, used to encapsulate logic and improve performance and maintainability.

📘 Quick Intro

Instead of repeating SQL code, you can write it once as a stored procedure and call it by name. This improves performance, helps manage complex logic, and enhances security by controlling data access.

🧠 Analogy / Short Story

Think of a stored procedure like a reusable recipe. Instead of rewriting how to bake a cake every time, you store the instructions and just say “follow the cake recipe.” It saves time, avoids mistakes, and ensures consistent results. Similarly, stored procedures help you reuse and standardize SQL logic in your database.

🔧 Technical Explanation

🛠️ Stored procedures are defined using CREATE PROCEDURE followed by the procedure name and logic.
📥 Parameters can be passed into procedures for dynamic behavior.
⚙️ They can include control flow, DML operations, loops, and conditions.
🔐 Procedures help abstract and secure database access from users or applications.
🔄 Execution is done using the EXEC or CALL statement (varies by SQL dialect).

🎯 Purpose & Use Case

✅ Reuse complex queries and logic across multiple applications.
✅ Control access to sensitive logic without exposing raw SQL to the client.
✅ Improve performance by pre-compiling logic.
✅ Use as part of data import/export pipelines or reporting logic.

💻 Real Code Example

-- Create a procedure (SQL Server syntax)
CREATE PROCEDURE GetCustomerOrders
                    @CustomerID INT
AS
BEGIN
    SELECT OrderID, OrderDate, TotalAmount
    FROM Orders
    WHERE CustomerID = @CustomerID;
END;

-- Execute the procedure
EXEC GetCustomerOrders @CustomerID = 5;

❓ Interview Q&A

Q1: What is a stored procedure?
A: It's a precompiled set of SQL statements stored in the database, designed for reuse and logic encapsulation.

Q2: Why use stored procedures?
A: To simplify code reuse, enhance security, improve performance, and manage complex SQL logic.

Q3: Can stored procedures take parameters?
A: Yes, they support input and output parameters to make them flexible.

Q4: Are stored procedures faster than raw queries?
A: Often, yes—they’re precompiled and optimized by the database engine.

Q5: What are common stored procedure dialects?
A: T-SQL (SQL Server), PL/pgSQL (PostgreSQL), PL/SQL (Oracle), and MySQL procedures.

Q6: Can a procedure return a result set?
A: Yes, it can return data via SELECT queries or OUT parameters.

Q7: How do you modify a stored procedure?
A: Use ALTER PROCEDURE or drop and recreate it depending on DBMS support.

Q8: What is the difference between stored procedures and functions?
A: Procedures don’t return a value directly like functions do, and they can perform actions like DML operations.

Q9: Can stored procedures call other procedures?
A: Yes, they can call other procedures or functions within their body.

Q10: Is error handling possible in stored procedures?
A: Yes, using TRY-CATCH (T-SQL), EXCEPTION blocks (PL/pgSQL), or DECLARE HANDLER (MySQL).

📝 MCQs

Q1. What is a stored procedure in SQL?

A temp table
A table backup
Reusable SQL code stored in the database
A static view

Q2. Which keyword creates a stored procedure in SQL Server?

MAKE PROC
CREATE FUNCTION
CREATE PROCEDURE
BEGIN PROCEDURE

Q3. How do you execute a stored procedure?

SELECT FROM
EXEC or CALL
RUN PROC
CALL FUNCTION

Q4. What is one advantage of using stored procedures?

Slower execution
Worse readability
Better code reuse and security
Prevents joins

Q5. What is the syntax to pass a parameter?

$param
#param
@paramName
:param

Q6. Do stored procedures support control flow?

No
Only in Oracle
Yes, including IF, WHILE, etc.
Only loops are allowed

Q7. Which statement is used to modify a stored procedure?

CHANGE PROC
UPDATE PROC
ALTER PROCEDURE
MODIFY FUNCTION

Q8. Can stored procedures include INSERTs and DELETEs?

No
Only SELECT
Yes
Only UPDATE

Q9. What is PL/pgSQL?

A data type
A function format
PostgreSQL’s procedural language
A MySQL tool

Q10. Are procedures stored on the client or server?

Client
Browser
Server
App memory

💡 Bonus Insight

Stored procedures can significantly reduce client-server traffic by bundling multiple SQL statements into a single call. Always test procedures with realistic data and use proper error handling to catch failures gracefully.

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How to Write Stored Procedures in SQL