Data Engineer Data Manipulation (SQL/Python) Interview Questions
Practice the exact questions companies are asking right now.
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Tackle Python tasks under time pressure
In a 15-minute coding round, implement a small Python function or class to solve a well-scoped problem within about 5 minutes of coding. 1) State 1–2 ...
Differentiate pandas objects and SQL filters
Python (pandas) 1. What is the difference between a pandas Series and a pandas DataFrame? - Discuss structure (1D vs 2D), indexing, column labels, ...
Recommend two-hop follows in Python
Given a directed "follows" graph as a Python dict[str, list[str]], implement recommend_two_hop(graph, user) that returns the set (or a sorted list) of...
Compute unique duration by merging intervals
Problem You have an autonomous-driving clip dataset where each row represents a time interval from a driving run. Table: clips | column | type | descr...
Explain pandas and SQL basics
You are interviewing for a Data Engineer co-op/intern role. Answer the following short technical questions. Python / pandas: 1. What is the difference...
Write SQL for active follow connections
Table: follow_events(requester_id INT, target_id INT, event STRING CHECK (event IN ('request_follow','follow_success','follow_reject','unfollow')), ev...
Solve three SQL problems (easy/medium/hard)
Answer the following SQL tasks of increasing difficulty: 1) Aggregation: Given Orders(order_id, customer_id, amount, order_date), return each customer...
Write SQL for library analytics
Given a library database, write SQL to answer the following: 1) Count the number of books that are currently not returned (i.e., still checked out) an...
Write PostgreSQL string-manipulation query
You are given a PostgreSQL table clickstream(session_id TEXT, page TEXT, query TEXT, ts TIMESTAMP). The page column contains full URLs like 'https://s...
Explain Pandas and SQL Basics
You are interviewing for a Data Engineer internship. Answer the following short data-manipulation questions: 1. In pandas, what is the difference betw...
Optimize SQL to minimize scans
Given a large analytics query, refactor it to minimize table scans. 1) Replace unnecessary CTEs that cause multiple scans with inline aggregations or ...
Debug a Hive Query for DAU
You are given two Hive tables: users(user_id BIGINT, created_at TIMESTAMP) and events(user_id BIGINT, event_time TIMESTAMP, event_name STRING) PARTITI...
Find customer with max rentals in consecutive weeks
You are given a table purchases(customer_id INT, purchase_date DATE, rented_copies INT). Consider only dates in calendar year 2024. Define a full week...
Find top 3 books by total borrowed time
Using copies(copy_id, book_id) and checkouts(copy_id, checkout_date, return_date), compute for each book_id the total borrowed duration as the sum ove...
Write Postgres string parsing and aggregation query
You are given a PostgreSQL table events(user_id TEXT, raw TEXT) where raw stores pipe-delimited key=value pairs, for example 'user=U1|country=US|ts=20...
Compute reservation diff for largest member
Given copies(copy_id, reserved_by_member_id) and members(member_id, referred_by_member_id), find the member with the largest member_id. Return a singl...
Solve library SQL and Python tasks
You are given a library domain. Assume these tables: - books(book_id, author_id, title) - authors(author_id, name) - copies(copy_id, book_id, conditio...
Solve Python and SQL data tasks
Complete both tasks: 1) Python: Implement a function flatten(nested) that takes a list whose elements are integers or arbitrarily nested lists of inte...
Return count and renewal percentage of unreturned good copies
Tables: copies(copy_id, condition), checkouts(copy_id, checkout_date, return_date, renewal_count). Write a single SQL query that returns one row with ...
Write SQL for library analytics
Given a library database, write SQL to answer: 1) How many books are in good condition and not returned? Among these books, what is the percentage tha...