Mastering ACID Properties in Databases with SQL
Every reliable database follows the ACID principles Atomicity, Consistency, Isolation, and Durability to ensure data remains accurate and dependable even under system failures.
In this blog, we’ll demonstrate ACID properties with SQL transactions using a simple Loan Management example.
Step 1: Setup the Schema
We’ll create a Loans table that stores customer loan detail
Enter the values to be inserted in the table
Display
Atomicity — “All or Nothing”
Concept: Either all statements in a transaction succeed, or none are applied
Update and roll back
Atomicity ensures no partial updates happen.
Consistency — “Valid Data Always”
Concept: The database should always remain in a valid state before and after a transaction.
Consistency ensures that invalid records (like negative dues) are never stored.
Isolation — “Transactions Work Independently”
Concept: When multiple users perform transactions at the same time, one should not see another’s uncommitted data.
Isolation ensures accurate reads — no dirty or uncommitted data is visible.
Durability — “Data That Stays Forever”
Concept: Once a transaction is committed, it remains even after a crash or restart.
Key Takeaways
Property | Meaning | SQL Feature Demonstrated
Atomicity | All or nothing | START TRANSACTION + ROLLBACK
Consistency | Data validity | CHECK constraint
Isolation | No interference | Parallel sessions
Durability | Data persistence | COMMIT survives restart
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