Essential SQL Interview Questions for Beginners

Updated 9 July 2026 · Intervuz

Introduction to SQL Interviews

Structured Query Language (SQL) is a critical skill for many data-related positions. Whether you're aiming for a role as a data analyst, database administrator, or software developer, understanding SQL is essential. This article aims to provide beginners with commonly asked SQL interview questions and their answers to help you prepare effectively.

1. What is SQL?

SQL stands for Structured Query Language. It is used for managing and manipulating relational databases. SQL allows users to perform tasks such as querying data, updating records, and managing database structures.

2. What are the different types of SQL commands?

SQL commands can be categorized into several types:

• DDL (Data Definition Language): Commands like CREATE, ALTER, and DROP that define database structures.
• DML (Data Manipulation Language): Commands like SELECT, INSERT, UPDATE, and DELETE that manipulate data within the database.
• DCL (Data Control Language): Commands like GRANT and REVOKE that control access to data in the database.
• TCL (Transaction Control Language): Commands like COMMIT and ROLLBACK that manage transactions in the database.

3. What is a primary key?

A primary key is a unique identifier for a record in a database table. It ensures that no two records have the same value in that field, which helps maintain data integrity. A table can only have one primary key, but it can consist of multiple columns (composite key).

4. Explain the difference between INNER JOIN and LEFT JOIN.

INNER JOIN returns only the rows that have matching values in both tables. In contrast, LEFT JOIN returns all the rows from the left table and the matched rows from the right table. If there is no match, NULL values are returned for the right table's columns.

5. What is a foreign key?

A foreign key is a field in one table that uniquely identifies a row in another table. It establishes a relationship between the two tables, enforcing referential integrity. A foreign key can accept duplicate values and can also be NULL.

6. How do you retrieve unique values from a column in SQL?

To retrieve unique values, you can use the SELECT DISTINCT statement. For example:

SELECT DISTINCT column_name FROM table_name;

7. What is an aggregate function?

Aggregate functions perform a calculation on a set of values and return a single value. Common aggregate functions include:

• COUNT: Counts the number of rows.
• SUM: Calculates the total sum of a numeric column.
• AVG: Computes the average value of a numeric column.
• MAX: Returns the maximum value.
• MIN: Returns the minimum value.

8. How do you filter records in SQL?

To filter records, you use the WHERE clause in your SQL query. For example:

SELECT * FROM table_name WHERE condition;

9. What is normalization?

Normalization is the process of organizing data in a database to reduce data redundancy and improve data integrity. It involves dividing large tables into smaller, related tables and defining relationships between them.

10. Why is it important to index a database?

Indexing a database improves the speed of data retrieval operations. An index is a data structure that allows the database management system to find records more quickly. However, while indexes speed up read operations, they can slow down write operations due to the need to maintain the index.

Conclusion

Preparing for an SQL interview as a beginner involves understanding fundamental concepts and practicing common queries. It's beneficial to practice answering these questions out loud to build confidence. You can use Intervuz, which features Vika, an AI interviewer, to simulate interview scenarios and refine your SQL skills.