10 The Trade Desk SQL Interview Questions (Updated 2024)

(Ex-Facebook & Best-Selling Data Science Author)

Updated on

March 3, 2024

At The Trade Desk, SQL does the heavy lifting for querying and analyzing advertising datasets, and managing and updating the audience and campaign databases. Unsurprisingly this is why The Trade Desk almost always asks SQL questions during interviews for Data Science, Analytics, and & Data Engineering jobs.

In case you're preparing for a SQL Interview, we've curated 10 The Trade Desk SQL interview questions to practice, which are similar to commonly asked questions at The Trade Desk – able to answer them all?

10 The Trade Desk SQL Interview Questions

SQL Question 1: Calculate the Daily Average Bid Amount

Let's suppose you are a data analyst at The Trade Desk, and you're given a dataset that records all the bids that the company placed in the last quarter. The data includes the date, campaign_ID, and bid amount. Your task is to write a SQL query to calculate the daily average bid amount per campaign for the last quarter.

Here are your sample data:

Example Input:

bid_id	campaign_id	bid_date	bid_amount
2271	567	12/02/2022	2.50
8912	789	12/02/2022	3.20
3784	567	12/03/2022	2.70
7423	789	12/03/2022	3.10
2837	567	12/04/2022	2.40

Solution:

The SQL window function you can use here is with the use of clause ordering by and partitioned by .

In PostgreSQL, your solution might look like this:

This calculates the average bud amount per campaign for each day in the specified date range, ordered by and . The clause ensures the average at each row is calculated using all the rows till the current one in each partition.

Example Output:

bid_date	campaign_id	daily_avg_bid
12/02/2022	567	2.50
12/03/2022	567	2.60
12/04/2022	567	2.53
12/02/2022	789	3.20
12/03/2022	789	3.15

This table indicates the daily average bid amount for each campaign across all the bidding dates in the last quarter.

To practice a similar problem on DataLemur's free online SQL code editor, try this Meta SQL interview question:

SQL Question 2: Ad Campaign Performance Evaluation

Assuming you are working as a Data Analyst at The Trade Desk, a company that specializes in programmatic advertising. Your company runs ad campaigns for various advertisers. Each campaign has multiple ads and these ads are displayed in different regions. Your goal is to evaluate the effectiveness of these campaigns based on some metrics such as the number of impressions and click-through rates (CTR).

These metrics are derived from the following tables:

table:

campaign_id	ad_id	advertiser_id
1	101	1
2	102	1
3	103	2
4	104	2
5	105	3

table:

ad_id	region_id
101	1
102	1
103	2
104	2
105	3

table:

ad_id	time_stamp	is_clicked
101	06/08/2022 00:00:00	1
102	06/10/2022 00:00:00	0
103	06/18/2022 00:00:00	1
104	07/26/2022 00:00:00	0
105	07/05/2022 00:00:00	1

The question here is to write an SQL query to calculate the average click-through rate (CTR) by campaign, advertiser, and region for all ads.

Please note that:

CTR is defined as the number of clicks divided by the number of impressions (i.e., each time an ad is shown) for each ad, and then you average it by campaign, advertiser, and region.
You should consider each row in the table as 1 impression.

Answer:

This query works by first joining the , , and tables on their common keys. It then groups by , , and . Finally, it calculates the average CTR by converting the value to float and taking the average grouped by each campaign, advertiser, and region.

To solve a similar problem about calculating rates, try this SQL interview question from TikTok on DataLemur's online SQL coding environment:

SQL Question 3: What are the three different normal forms?

The three levels of database normalization (also known as normal forms) are:

First Normal Form (1NF):

Each column should contain the same type of data (no mixing strings vs. integers)
Each column in a table contains a single value (no lists or containers of data)
Each row in the table is unique

Second Normal Form (2NF)

It's in 1st Normal Form
All non-key attributes are dependent on the primary key

Said another way, to achieve 2NF, besides following the 1NF criteria, the columns should also be dependent only on that table's primary key.

Third normal form (3NF) if it meets the following criteria:

It's in 2nd Normal Form
There are no transitive dependencies in the table.

A transitive dependency means values in one column are derived from data in another column. For example, it wouldn't make sense to keep a column called ""vehicle's age"" and ""vehicle's manufacture date" (because the vehicle's age can be derived from the date it was manufactured).

Although there is a 4NF and 5NF, you probably don't need to know it for the The Trade Desk interview.

The Trade Desk SQL Interview Questions

SQL Question 4: Filter Customers Based on Campaign Interaction

As part of the marketing analytics team at The Trade Desk, you're required to filter out customers who have both clicked on a specific marketing campaign and made a purchase within 30 days of the campaign. Date of campaign interaction and date of purchase should both be in the year 2022. Use the following tables for this analysis: