Capital One Data Scientist Data Manipulation (SQL/Python) Interview Questions
Practice 23 real Data Manipulation (SQL/Python) interview questions for Data Scientist roles at Capital One.
"I got asked a hardcore MCM DP question and I saw it on PracHub as well. Solved that question in 5 minutes. Without PracHub I doubt I could solve it in 5 hours. Though somehow didn't get hired, perhaps I guess I solved it too fast? /s"
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"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Clean and Merge Housing Data
This question evaluates data cleaning, type coercion, robust merge operations, and missing-data imputation skills within tabular datasets, emphasizing...
Fix dash dates and aggregate watch time
You receive a CSV of ad viewing logs where the date column repeats only on the first row of each block and subsequent rows use a single dash '-' to in...
Determine Country with Most 'Sunny' Days
Weather +------------+------------+---------+ | country | date | weather | +------------+------------+---------+ | Spain | 2023-07-01 | ...
Audit flight data quality from metadata
You’re given an airline on‑time dataset and a one‑page “Metadata” slide that claims: flight_date (string, local time), dep_time/arr_time (HHMM local),...
Write SQL to compute campaign net revenue
Using the schema and sample data below, write SQL to produce, for each campaign_id and segment, the following metrics for August 2025: total_reached, ...
Write SQL for lowest price with ratings
You have two tables. Schema: - products(product_id INT PRIMARY KEY, product_name TEXT, category TEXT) - purchase(purchase_id INT PRIMARY KEY, product_...
Merge CSVs and build revenue pivot with pandas
You receive four CSVs and must replicate an Excel VLOOKUP + PivotTable workflow using Python/pandas. CSV samples: customers.csv customer_id,signup_dat...
Reconcile ledgers with SQL/Python and late events
You own a daily ETL + reconciliation job between two financial ledgers. Late postings (“delay time”) up to 48 hours are common. Schema: - payments_raw...
Impute missing values without leakage
Given a DataFrame df with columns: user_id, event_date (datetime), country (categorical), device_type (categorical), age (numeric), income (numeric), ...
Merge seven tables into one clean DataFrame
Using pandas only (no loops over rows), write a function build_facts(customers, orders, order_items, products, payments, shipments, refunds) -> pd.Dat...
Compute Customer Spend and Engineer Features for 2023
transactions +-----------+-------------+--------+------------+--------------+ | tran_id | customer_id | amount | tran_date | merchant_cat | +------...
Merge four CSVs locally, robustly and efficiently
You receive four CSV files that must be merged locally on a laptop with 8 GB RAM, without relying on cloud services: - products.csv: product_id, categ...
Merge ad CSVs and compute CTR
Using SQL, clean and merge four CSVs and answer all parts exactly. Schema and sample rows (assume types: date is DATE, others INT/VARCHAR): platforms(...
Aggregate exam scores with NULL handling
Write a single SQL query (or CTE pipeline) to satisfy all requirements using the schema and sample data below. Replace any vendor-specific function wi...
Calculate Longest Transaction Streak for Each User
transactions +---------------+---------+--------+----------------+-----------+----------+ | transaction_id| user_id | amount | transaction_date| merch...
Find top category per region in Aug 2025
You are given the following schema and sample data. Schema: - customers(customer_id INT, name TEXT, region TEXT) - orders(order_id INT, customer_id IN...
Write SQL for theme-park revenue and visits
You are given theme-park ticketing and visits data. Write SQL to answer the following, using the sample schema and tables below. Return both the query...
Identify country with highest sunny-day probability
Write SQL to find the country with the highest probability that a day is sunny. Use the schema and sample data below. Rules: consider a day sunny for ...
Write SQL to find top net-revenue products
Using the sample schema and data below, write a single SQL query that returns, for the last 7 days relative to today (use today = 2025-09-01, so the w...
Write SQL to quantify outage revenue loss
A database outage blocked premium membership registrations from 2025-01-01 to 2025-03-31 (inclusive). Members intend to start on intended_start_date, ...