SQL interview Questions For Aspiring Data Scientist — The Histogram

Histograms

The histogram question is a general warm up question for aspiring data scientist a bit akin to fizz buzz for Software engineering.

It is a step that needs to be repeated countless time in the life of a data-scientist to get a sense of a distribution of different variables and which is not very difficult technically.

Any seasoned data-scientist should be able to do these step out of top of their mind and aspiring data-scientist should be able to prove they have the technical knowledge to do these.

Questions

Given an order item table containing the following fields:

order_item:
	order_date DATE,
	order_id INT,
        user_id INT,
	order_item_id INT,
	catalog_item_id INT,
	item_quantity INT,
	item_price INT

1) Provide an histogram of item price
2) Provide an histogram of orders by order price

Answer 1)

SELECT
    item_price,
    COUNT(1) as frequency
FROM order_item
GROUP BY 1

This is traditionally a warm up question to just check if the candidate has some bases on SQL and can actually use a group by clause.