# 10 Flywire SQL Interview Questions (Updated 2024)

Updated on

March 3, 2024

At Flywire, SQL is typically used for analyzing and reporting on international payment transaction data, and maintaining the customer financial database for optimized payment solutions. Unsurprisingly this is why Flywire asks SQL query questions during interviews for Data Analyst, Data Science, and BI jobs.

So, to help you prepare for the Flywire SQL interview, this blog covers 10 Flywire SQL interview questions – able to answer them all?

## 10 Flywire SQL Interview Questions

### SQL Question 1: Calculate Monthly Average Transaction Amount

Flywire is an international payment solution. One day, the data scientist team wants to know the monthly average transaction amount for each country to identify the trends and patterns. They provide you with the following dataset and ask you to write a SQL query using window functions to calculate the monthly average transaction amount for each country, sorted by country and year-month in ascending order.

##### Example Input:
transaction_idclient_idtransaction_datecountrytransaction_amount
23593432022-01-15USA250.50
49201572022-02-06CAN500.00
21348962022-01-22CAN233.00
65329202022-02-14USA460.75
91231252022-02-25CAN600.00

This SQL query first creates a window for each month and country, then calculates the average transaction amount within each window. The result is then grouped by country and year-month. Finally, the result is ordered by country and year-month in ascending order. The function is used to limit the average transaction amount to two decimal places.

To practice a related window function SQL problem on DataLemur's free online SQL code editor, solve this Google SQL Interview Question:

### SQL Question 2: Flywire Transactions Analysis

Flywire serves millions of clients facilitating cross-border transactions. You have two tables containing relevant data. One table, 'clients', contains their user_id, client name and country. Another table, 'transactions', includes each transaction's id, the sender's user_id, the receiver's user_id, the transaction's date and transaction's amount.

Design a SQL query that will output the total transactions amount each client has received per month, sorted by the transaction amount in descending order.

##### Example Input:
user_idclient_namecountry
1John S.USA
2Maria G.Spain
3Tom K.UK
##### Example Input:
11206/08/2022500
23106/08/20221000
31306/08/2022400
42406/09/2022600
54107/10/2022350
63207/15/20221200
74307/20/2022700

The following PostgreSQL query can be used to answer this question:

In this query, first a CTE (Common Table Expression) named is created to aggregate the total transaction amount that each user has received per month. Then, this CTE is joined with table on receiver_id to get the client's name. The final list is sorted by the transaction amount in descending order to arrange the clients according to how much they have received.

### SQL Question 3: How do you select records without duplicates from a table?

If you want to return records with no duplicates, you can use the keyword in your statement.

For example, if you had a table of Flywire employees, and wanted to see what are all the unique job titles that currently worked at the company, you could write the following query:

If had the following data:

f_namejob_title
AkashData Analyst
BrittanyData Scientist
CarlosData Engineer
DiegoData Engineer

Then the output from the query would be:

job_title
Data Analyst
Data Scientist
Data Engineer

### SQL Question 4: Calculate the Average Transaction Amount per Currency

Flywire, a global payment solution company, is interested to understand more about their transactions. Your task is to calculate the average transaction amount for each type of currency over a certain period.

##### Example Input:
transaction_idtransaction_datecurrencyamount
10101/02/2022USD250.00
30501/07/2022EUR150.00
80302/11/2022USD500.00
20402/21/2022EUR300.00
50502/29/2022GBP100.00
##### Example Output:
monthcurrencyavg_transaction
1USD250.00
1EUR150.00
2USD500.00
2EUR300.00
2GBP100.00

This PostgreSQL query uses the function to calculate the average transaction amount by currency and month. The function is applied to the column to extract the month of the transactions. The result is grouped by currency and month and ordered by month and currency for easy reading.

To practice a very similar question try this interactive Stripe Repeated Payments Question which is similar for requiring analysis of transaction data or this Uber User's Third Transaction Question which is similar for focusing on individual transaction records.

### SQL Question 5: What does do in a SQL query?

is used to combine the results of multiple statements into a single result set.

Suppose you were doing an HR Analytics project for Flywire, and needed to analyze both Flywire's contractors and employees. You could use in the following way:

This statement would return a combined result set of Flywire contractors and employees who were hired after the start of the year 2023.

### SQL Question 6: Calculate Click-Through-Rate on Flywire's Marketing Campaigns

Flywire has been running different marketing campaigns to attract more customers. For each ad displayed to a user, Flywire tracks whether the user clicked on the ad and whether the user subsequently purchased a service after clicking the ad.

Given two tables and , calculate the click-through rate (CTR) and the conversion rate. The click-through rate is defined as the number of clicks divided by the number of impressions, and the conversion rate is defined as the number of purchases divided by the number of clicks.

Assume we track the following information:

table:

• (unique identifier for each ad)
• (unique identifier for each user)
• (time when the ad was displayed)
• (whether the ad was clicked: 1 - clicked, 0 - not clicked)

table:

• (unique identifier for each purchase)
• (unique identifier for each user)
• (unique identifier for the ad that led to the purchase)
• (time when the purchase was made)
##### Sample Input:
10112306/08/2022 00:00:001
10226506/10/2022 00:00:000
10336206/18/2022 00:00:001
10419207/26/2022 00:00:000
10598107/05/2022 00:00:001
##### Sample Input:
100112310106/08/2022 01:00:00
100236210306/18/2022 02:00:00
100398110507/05/2022 03:00:00

In the SQL query, we first join 'ads' and 'purchases' table on 'ad_id' and 'user_id' to combine the click and purchase information for each user.

Then in the SELECT clause:

• We calculate the click-through rate (CTR) by summing up 'clicked' (i.e., the number of clicks) and divide by the total number of rows (i.e., the number of impressions). Since 'clicked' only contains 0's and 1's, summing 'clicked' gives the total number of clicks.
• We calculate the conversion rate by first counting the number of 'purchase_id', which gives the total number of purchases, then divide by the total number of clicks. We use the SUM function again on 'clicked' to calculate the total number of clicks.

To solve a similar problem about calculating rates, solve this TikTok SQL question within DataLemur's online SQL code editor:

### SQL Question 7: In SQL, Are NULL values the same as a zero or blank space?

{#Question-7}

In SQL, a value is NOT the same as a zero or a blank space. A NULL value represents the absence of a value or a missing value, whereas both zero and blank space are actually values.

To handle nulls, the function is often used to check for a null, and if there is a null, you can assign a default value.

### SQL Question 8: Average Transaction Value Per Country

Flywire facilitates international payments. As part of a business review, you need to understand the average transaction value per country over a certain period (e.g., monthly basis). This could help to identify countries with high-value transactions, a potentially interesting piece of information for the business strategy.

##### Example Input:
transaction_iduser_idtransaction_datecountry_idamount
134506/10/2022 00:00:001013000
256706/10/2022 00:00:001014000
389006/20/2022 00:00:001025000
456707/10/2022 00:00:001014000
589007/20/2022 00:00:001029000
##### Example Output:
mthcountryavg_transaction
61013500
61025000
71014000
71029000

This SQL query does the following:

1. extracts the month from for each transaction.
2. renames to for readability in the output.
3. calculates the average transaction value for the and grouping.
4. orders transactions such that transactions that belong to the same and are grouped together. Within these groups, the average transaction value is computed.

### SQL Question 9: Find Customer Records

As a data analyst at Flywire, you've been tasked with retrieving customer records from the company database. Specifically, the marketing team is running a promotional event for customers with Gmail addresses. They want a list of all customers whose emails are registered with Gmail. Write a SQL query to filter the customer data and output these details: customer id, customer name, and email id.

##### Example Input:
customer_idcustomer_nameemail_id
001John Doejohn.doe@gmail.com
002Jane Smithjanesmith@yahoo.com
003James Brownjbrown@hotmail.com
004Jessica Jonesjjones@gmail.com
005Tom Hankstom.hanks@yahoo.com
##### Example Output:
customer_idcustomer_nameemail_id
001John Doejohn.doe@gmail.com
004Jessica Jonesjjones@gmail.com

This SQL query uses the LIKE operator to filter and return records from the customers table where the 'email_id' ends with '@gmail.com', indicating the customer is using a Gmail account. The percentage sign (%) serves as a wildcard character, which means any characters can precede '@gmail.com'.

### SQL Question 10: How can you identify duplicates in a table? Do have any other approaches?

"One creative way is to use the window function ROW_NUMBER() and partition by whichver columns you are loooking for duplicates in. If any row has a row_number() more than 1, then it's a duplicate!

You could also use COUNT(DISTINCT col1) vs. COUNT(*) and see if they return different numbers, indicating the prescence of duplicates!

### Flywire SQL Interview Tips

The best way to prepare for a SQL interview, besides making sure you have strong SQL fundamentals, is to practice a ton of real SQL questions that were asked in recent job interviews. Beyond just solving the earlier Flywire SQL interview questions, you should also solve the 200+ SQL questions on DataLemur which come from companies like Microsoft, Google, and Facebook.

Each DataLemur SQL question has multiple hints, fully explained answers along with a discussion board to see how others solved it and crucially, there's an interactive SQL code editor so you can right online code up your query and have it graded.

To prep for the Flywire SQL interview you can also be useful to practice SQL problems from other tech companies like:

In case your SQL foundations are weak, don't worry about jumping right into solving questions – strengthen your SQL foundations with this SQL tutorial for Data Scientists & Analysts.

This tutorial covers SQL concepts such as finding NULLs and window functions like RANK() and ROW_NUMBER() – both of these come up routinely in Flywire interviews.

### Flywire Data Science Interview Tips

#### What Do Flywire Data Science Interviews Cover?

In addition to SQL interview questions, the other types of problems to practice for the Flywire Data Science Interview are:

#### How To Prepare for Flywire Data Science Interviews?

The best way to prepare for Flywire Data Science interviews is by reading Ace the Data Science Interview. The book's got:

• 201 Interview Questions from Facebook, Google & startups
• A Crash Course covering Stats, ML, & Data Case Studies
• Amazing Reviews (900+ reviews, 4.5-star rating)