Interview Q&A

nd does not log individual row deletions.

• Cannot be rolled back (in most databases).
• Resets auto-increment counters.
• DELETE: Deletes rows based on a condition, and can be rolled back (if using

transactions).

• Slower compared to TRUNCATE.

Example:

DELETE FROM Employees WHERE Age < 18; -- Deletes only specific rows

TRUNCATE TABLE Employees; -- Deletes all rows

• TRUNCATE: Deletes all rows in a table, but the table structure remains. It is faster

and does not log individual row deletions.

• Cannot be rolled back (in most databases).
• Resets auto-increment counters.
• DELETE: Deletes rows based on a condition, and can be rolled back (if using

transactions).

• Slower compared to TRUNCATE.

Example:

DELETE FROM Employees WHERE Age < 18; -- Deletes only specific rows

TRUNCATE TABLE Employees; -- Deletes all rows

n Index is a database object that speeds up the retrieval of rows from a table by creating a

data structure (often a B-tree). Indexes improve the performance of SELECT queries but can

slow down INSERT, UPDATE, and DELETE operations.

Example:

CREATE INDEX idx_employee_name ON Employees(Name);

The ACID properties ensure reliable processing of database transactions:

What interviewers expect

• A clear definition tied to SQL in SQL & Databases projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production SQL & Databases application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in SQL & Databases architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.