10 Wells Fargo SQL Interview Questions (Updated 2024)

Updated on

June 30, 2024

Wells Fargo employees write SQL queries often for analyzing transactional data to detect fraudulent activity and managing customer databases. For this reason Wells Fargo almost always asks SQL coding questions in interviews for Data Science, Analytics, and & Data Engineering jobs.

So, to help you prep, here's 10 Wells Fargo SQL interview questions – able to answer them all?

Wells Fargo SQL Interview Questions

10 Wells Fargo SQL Interview Questions

SQL Question 1: Identify the Top 10 VIP Customers for Wells Fargo

As a data analyst for Wells Fargo, your task is to write a SQL query that identifies the top 10 customers who have carried out the most transactions in the last year. Transactions can include deposits, withdrawals, funds transfers, and purchases via debit cards.

The Customers and Transactions tables are structured as follows:

Example Input:
Example Input:

Note that a transaction_id is unique across all transactions, and it corresponds to a specific customer who carries out the transaction.


You might craft a query like the following:

This PostgreSQL query would return the first and last names of the 10 customers who have performed the most transactions within the past year. The function returns the first day of the current year, and the clause restricts the output to the top 10 customers. The customers are sorted in descending order by the count of their transactions.

If two or more customers share the same transaction count, they may appear in any order within the top 10 list. Use other sorting criteria in the clause if you want a deterministic order among these customers.

To practice a similar customer analytics SQL question where you can solve it right in the browser and have your SQL query automatically checked, try this Walmart SQL Interview Question: Walmart SQL Interview Question

SQL Question 2: Second Highest Salary

Given a table of Wells Fargo employee salaries, write a SQL query to find the 2nd highest salary among all employees.

Wells Fargo Example Input:


Example Output:


You can solve this problem directly within the browser on DataLemur:

2nd Highest Salary SQL Interview Question


You can find a detailed solution with hints here: 2nd Highest Salary.

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

The keyword removes duplicates from a query.

Suppose you had a table of Wells Fargo customers, and wanted to figure out which cities the customers lived in, but didn't want duplicate results.



You could write a query like this to filter out the repeated cities:

Your result would be:


Wells Fargo SQL Interview Questions

SQL Question 4: Analysis of Monthly Loan Defaults

Assume that you have been hired as a Data Scientist at Wells Fargo. The company is concerned about the number of loans going default each month. Your task is to write a SQL query that can help the management understand the pattern of loan defaults by providing them with the average, maximum and minimum loan amounts that default each month.

Here's an example of the dataset:

Example Input:

In this task, we need to analyze the table and find out the average, maximum and minimum loan amounts that default () on a monthly basis.


The SQL query for the task would be:

The above query uses window functions to calculate the average, maximum and minimum loan amounts per month where the loan has defaulted. The PARTITION BY clause is used with the window function to calculate these values for each month individually. The WHERE clause filters out the loans which have not defaulted. Finally, we order the result by the month.

This SQL query will provide the management at Wells Fargo with insights about the pattern of loan defaults in terms of the average, minimum, and maximum loan amounts on a monthly basis.

To practice a related window function SQL problem on DataLemur's free online SQL coding environment, try this Google SQL Interview Question: Google SQL Interview Question

SQL Question 5: How would you speed up a slow SQL query?

There's several steps you can take to troubleshoot a slow SQL query.

First things first, figure out why the query is slow! You can use and commands in PostgreSQL to identify any performance bottlenecks. After that, you can start changing your query, depending on what the source of the query performance issue is.

Generally, indexes can help speed up queries. Also de-normalizing your tables might help, to remove slow joins.

Lastly, you could always just upgrade your hardware! Time and money wasted improving query performance could just be better spent on mroe powerful database servers!

While this is a very surface-level approach to optimizing SQL query performance, it should do the trick for Data Analyst interviews and Data Science interviews at Wells Fargo. Data Engineers should know a bit more about the and before the interview.

SQL Question 6: Filter Out Specific Customers' Details

You are a data analyst at Wells Fargo. The marketing team has requested a list of customer details. They want to know the customers who live in California or New York and have an account balance greater than 10,000 dollars and those who have withdrawn more than 2000 dollars or deposited more than 5000 dollars in the last year.

Example Input:
98795JaneSmithNew York19000
32254AnaPerryNew York20000
Example Input:


This query first joins the Customers and Transactions tables on the Customer_id. It then filters based on the conditions given: the state of the customer (California or New York), the account balance (>10000), the type and amount of transactions (withdrawn >2000 or deposited >5000 in last year). The result is a list of customers who meet these criteria.

SQL Question 7: What do the SQL commands / do?

For a tangible example of in PostgreSQL, suppose you were doing an HR Analytics project for Wells Fargo, and had access to Wells Fargo's contractors and employees data. Assume that some employees were previously contractors, and vice versa, and thus would show up in both tables.

You could use operator to find all contractors who never were a employee using this query:

Note that is available in PostgreSQL and SQL Server, while is the equivalent operator which is available in MySQL and Oracle (but don't worry about knowing which RDBMS supports which exact commands since Wells Fargo interviewers aren't trying to trip you up on memorizing SQL syntax).

SQL Question 8: Average Account Balance by Customer

At Wells Fargo, you are given a database with tables pertaining to customer accounts. Your task is to write a SQL query to compute and return the average balance for each customer.

The table has the following columns:

  1. account_id (integer): unique identifier for each account.
  2. customer_id (integer): unique identifier for each customer.
  3. balance (float): the current balance of the account.

Here's a markdown-formatted sample of the table:

Example Input:
Example Output:


This query groups the accounts by customer and computes the average balance. Each row in the output corresponds to a customer, and it contains the customer_id together with their average account balance.

To practice a very similar question try this interactive Amazon Highest-Grossing Items Question which is similar for aggregation and ranking or this Amazon Average Review Ratings Question which is similar for computing averages.

SQL Question 9: Wells Fargo Average Loan Amount by Month

As a data analyst for Wells Fargo, your job is to analyze loan data to provide business insights. You need to write a SQL query to find out the average loan amount approved each month, during the year 2022. This would help your team to understand the lending pattern and its variability over the year.

Please use the below sample table, , for this purpose.

Example Input:


This query extracts the month from the column and then groups the data by this month value. It then uses the function to calculate the average loan amount for each month over data from year 2022. The result from this query will show the average loan amount Wells Fargo has approved each month in the year 2022.

Check out Wells Fargo's Advanced Analytics and Data Program if you're looking to improve your analytics skills.

SQL Question 10: What's the difference between a unique index and non-unique index?

While both types of indexes improve the performance of SQL queries by providing a faster way to lookup rows of data, a unique index enforces the uniqueness of the indexed columns, meaning that no duplicate values are allowed in the indexed columns. On the other hand, a non-unique index allows duplicate values in the indexed columns.

Here is an example of a unique index on the column of a table of Wells Fargo employees:

This index would ensure that no two Wells Fargo employees have the same , which could be used as a unique identifier for each employee.

Here is an example of a non-unique index on the column of the same table:

This index would not enforce uniqueness, but it could be used to improve the performance of queries that filter or sort the data based on the column. For example, if you want to retrieve all employees who were Data Analysts, the database can use the index to quickly locate and retrieve the desired records without having to search through all the employees.

Wells Fargo 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. In addition to solving the earlier Wells Fargo SQL interview questions, you should also solve the 200+ SQL exercises on DataLemur which come from companies like Google, Facebook, Microsoft and Amazon. DataLemur Questions

Each interview question has multiple hints, detailed solutions and most importantly, there is an interactive SQL code editor so you can right in the browser run your SQL query answer and have it graded.

To prep for the Wells Fargo SQL interview it is also useful to solve SQL problems from other banking & finanacial services companies like:

But if your SQL coding skills are weak, forget about diving straight into solving questions – strengthen your SQL foundations with this SQL interview tutorial.

SQL tutorial for Data Analytics

This tutorial covers SQL concepts such as handling NULLs in SQL and 4 types of JOINS – both of which come up frequently in Wells Fargo SQL assessments.

Wells Fargo Data Science Interview Tips

What Do Wells Fargo Data Science Interviews Cover?

Beyond writing SQL queries, the other question categories covered in the Wells Fargo Data Science Interview include:

Wells Fargo Data Scientist

How To Prepare for Wells Fargo Data Science Interviews?

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

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