Mastering Google SQL Coding Interviews: A Comprehensive Collection of Interview Questions

As one of the tech giants in the world, Google is known for its rigorous interview process, particularly in roles that involve data analysis and manipulation. SQL, or Structured Query Language, is a fundamental tool in the realm of data management, and mastering it can significantly increase your chances of landing your dream job at Google. In this article, we’ll dive into a collection of Google SQL coding interview questions, providing you with the necessary preparation to tackle these challenges with confidence.

Understanding Google’s SQL Interview Process

Before we delve into the questions, let’s briefly discuss the SQL interview process at Google. SQL questions typically arise during the technical screen and on-site interview stages. During the technical screen, you can expect basic SQL questions, including definitions of concepts like JOIN, GROUP BY, and DATE functions. The on-site interview will likely involve more advanced SQL questions, requiring you to write complex queries using CASE statements, subqueries, and JOIN clauses.

A Comprehensive Collection of Google SQL Coding Interview Questions

  1. Explain the different types of joins in SQL.

    • INNER JOIN: Returns rows from both tables where the join condition is met.
    • LEFT JOIN: Returns all rows from the left table and matching rows from the right table.
    • RIGHT JOIN: Returns all rows from the right table and matching rows from the left table.
    • FULL JOIN: Returns all rows from both tables, regardless of whether the join condition is met or not.
  2. What is the PRIMARY KEY in SQL?
    A PRIMARY KEY is a column or a combination of columns that uniquely identifies each record in a table. It enforces entity integrity by ensuring that no duplicate values can be stored in the designated column(s). Primary keys cannot have NULL values, and each value must be unique.

  3. What are constraints?
    Constraints in SQL are rules or conditions that are applied to data columns within a table. They help maintain data integrity and consistency. Some common constraints include:

    • NOT NULL: Ensures that a column cannot have NULL values.
    • UNIQUE: Ensures that all values in a column are unique.
    • PRIMARY KEY: A combination of NOT NULL and UNIQUE constraints, ensuring that each row in a table is uniquely identified.
    • FOREIGN KEY: Establishes a link between two tables, ensuring referential integrity.
  4. What’s the difference between DELETE and TRUNCATE statements in SQL?

    • DELETE is a Data Manipulation Language (DML) statement that removes specific rows from a table based on a specified condition. It is a row-level operation, and the deleted data can be rolled back.
    • TRUNCATE is a Data Definition Language (DDL) statement that removes all rows from a table. It is a table-level operation, and the data cannot be rolled back. TRUNCATE is generally faster than DELETE as it does not log individual row deletions.
  5. What is query optimization?
    Query optimization is the process of restructuring SQL queries to improve their performance and efficiency. It involves analyzing the query structure, indexing strategies, and data distribution to find the most optimal execution plan. Query optimization aims to minimize resource utilization (CPU, memory, I/O) and reduce query execution time, ultimately enhancing database performance.

  6. Given the tables below, select the top three departments with at least ten employees and rank them according to the percentage of their employees making over $100,000 in salary.


    employees tableColumns: id, first_name, last_name, salary, department_iddepartments tableColumns: id, name

    Expected output:

    percentage_over_100K department name number of employees
    0.9 engineering 25
    0.5 marketing 50
    0.12 sales 12
  7. Given a users table, write a query to get the cumulative number of new users added by day, with the total reset every month.


    users tableColumns: id, name, created_at

    Expected output:

    Date Monthly Cumulative
    2020-01-01 5
    2020-01-02 12
    2020-02-01 8
    2020-02-02 17
    2020-02-03 23
  8. Given a table of product subscriptions with a subscription start date and end date for each user, write a query that returns true or false whether or not each user has a subscription date range that overlaps with any other user.


    subscriptions tableColumns: user_id, start_date, end_date

    Example input:

    user_id start_date end_date
    1 2019-01-01 2019-01-31
    2 2019-01-15 2019-01-17
    3 2019-01-29 2019-02-04
    4 2019-02-05 2019-02-10

    Expected output:

    user_id overlap
    1 1
    2 1
    3 1
    4 0
  9. Given a table of students and their SAT test scores, write a query to return the two students with the closest test scores with the score difference. If there are multiple students with the same minimum score difference, select the student name combination that is higher in the alphabet.


    scores tableColumns: id, student, score


    id student score
    1 Jack 1700
    2 Alice 2010
    3 Miles 2200
    4 Scott 2100


    one_student other_student score_diff
    Alice Scott 90
  10. We’re given two tables, a users table with demographic information and the neighborhood they live in and a neighborhoods table. Write a query that returns all of the neighborhoods that have 0 users.


    users tableColumns: id, name, neighborhood_id, created_atneighborhoods tableColumns: id, name, city_id

    Expected output:

    [Neighborhood names with 0 users]
  11. Given a table of transactions and products, write a query to return the product id, product price, and average transaction price of all products with price greater than the average transaction price.


    transactions tableColumns: id, user_id, created_at, product_id, quantityproducts tableColumns: id, name, price
  12. Let’s say we have two tables, transactions and products. Hypothetically, the transactions table consists of over a billion rows of purchases bought by users. We are trying to find paired products that are often purchased together by the same user, such as wine and bottle openers, chips and beer, etc. Write a query to find the top five paired products and their names. Note: for the purposes of satisfying the test case, P1 should be the item that comes first in the alphabet.


    transactions tableColumns: id, user_id, created_at, product_id, quantityproducts tableColumns: id, name, price

    Expected output:

    P1 P2 count
    [Product name 1] [Product name 2] [Count of paired purchases]

By practicing and mastering these Google SQL coding interview questions, you’ll be well-prepared to showcase your SQL proficiency and stand out in the competitive interview process at Google. Remember, preparation is key, and dedicating time to hone your SQL skills will undoubtedly increase your chances of success.

Google SQL Interview Question | Step By Step Solution


Does Google ask SQL questions in interview?

Google almost always asks SQL problems during interviews for Data Analytics, Data Science, and Data Engineering jobs. To help you land your dream job in data at Google, practice these 13 REAL Google SQL interview questions which we’ve curated and solved for you.

Related Posts

Leave a Reply

Your email address will not be published. Required fields are marked *