Demonstrating the SERIALIZABLE Isolation Level in MySQL

Demonstrate Serializable Isolation Level

Write a MySQL query to demonstrate the SERIALIZABLE isolation level by preventing phantom reads.

Solution:

-- Set the transaction isolation level to SERIALIZABLE
-- This is the strictest isolation level, ensuring full data consistency.
-- No other transaction can modify or insert rows that affect this query while the transaction is active.
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

-- Start a new transaction
START TRANSACTION;

-- Select all employees from DepartmentID = 2
-- Due to the SERIALIZABLE isolation level, other transactions cannot:
--  1. Modify existing employee records in DepartmentID = 2
--  2. Insert new employees into DepartmentID = 2 until this transaction is committed or rolled back.
SELECT * FROM Employees WHERE DepartmentID = 2;

-- Commit the transaction
-- This releases the SERIALIZABLE lock, allowing other transactions to proceed.
COMMIT;

Explanation:

• Purpose of the Query:
• The goal is to demonstrate how SERIALIZABLE prevents phantom reads.
• Key Components:
• SET TRANSACTION ISOLATION LEVEL SERIALIZABLE: Ensures complete isolation.
• Why use Serializable?:
• It prevents dirty reads, non-repeatable reads, and phantom reads.
• Real-World Application:
• For example, in a financial system, you might use SERIALIZABLE for critical operations.

For more Practice: Solve these Related Problems:

• Write a MySQL query that prevents phantom reads in a hotel reservation system using SERIALIZABLE isolation.
• Write a MySQL query that ensures no new records are inserted while a transaction is processing aggregated sales data.
• Write a MySQL query demonstrating how SERIALIZABLE isolation affects concurrent inserts and updates in a job application portal.
• Write a MySQL query that locks an entire table to prevent inconsistent reads when calculating total department expenses.

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