8 Iron Mountain SQL Interview Questions (Updated 2024)
At Iron Mountain, SQL is crucial for analyzing and managing vast repositories of data files, and optimizing storage management. That's the reason behind why Iron Mountain LOVES to ask SQL questions during interviews for Data Science, Data Engineering and Data Analytics jobs.
To help you practice for the Iron Mountain SQL interview, we've collected 8 Iron Mountain SQL interview questions in this blog.
8 Iron Mountain SQL Interview Questions
SQL Question 1: Identify the Most Active Customers at Iron Mountain
Iron Mountain Incorporated is an American enterprise information management service company, and they deal with services like records management, data backup and recovery, document management, etc. For such a company, active power users could be those customers who have the most transactions in terms of services availed like data backup, document management, etc.
Assuming the business designates customers as when they have more than 50 transactions in a month, write a SQL query that retrieves all from the customer transaction database for the month of June 2022.
The input will be polled from two tables: and .
Example Input:
| customer_id | customer_name |
|---|---|
| 102 | James |
| 280 | Olivia |
| 364 | Michael |
| 151 | Emma |
| 489 | Daniel |
Example Input:
| transaction_id | customer_id | transaction_date | service_id |
|---|---|---|---|
| 9001 | 102 | 06/15/2022 00:00:00 | 1111 |
| 9002 | 280 | 06/16/2022 00:00:00 | 2222 |
| 9003 | 364 | 06/17/2022 00:00:00 | 3333 |
| 9004 | 102 | 06/18/2022 00:00:00 | 4444 |
| 9005 | 364 | 06/19/2022 00:00:00 | 1111 |
Answer:
The following PostgreSQL script would find the VIP Users for the month of June 2022:
The query first joins the table and table on the . It then groups the result by both and . The clause is used here to only include those customers who have more than 50 transactions in June 2022 in the final result. If a customer fulfills this condition, they are considered a .
To solve a related super-user data analysis question on DataLemur's free online SQL code editor, try this recently asked Microsoft SQL interview question:
SQL Question 2: Second Highest Salary
Given a table of Iron Mountain employee salaries, write a SQL query to find the 2nd highest salary at the company.
Iron Mountain Example Input:
| employee_id | salary |
|---|---|
| 1 | 2500 |
| 2 | 800 |
| 3 | 1000 |
| 4 | 1200 |
Example Output:
| second_highest_salary |
|---|
| 1200 |
Test your SQL query for this question and run your code right in DataLemur's online SQL environment:
Answer:
You can find a detailed solution with hints here: 2nd Highest Salary.
BTW Iron Mountain has data centers all around the US, see if there is a Iron Mountain data center near you!
SQL Question 3: What are the different types of database indexes?
A database index is a way to optimize the performance of a database by reducing the amount of data that needs to be searched to retrieve a record.
There are several types of indexes:
- unique & non-inuqie indexes
- primary & composite indexes
- clustered & non-clustered indexes
SQL Question 4: Calculate Average Monthly Consumption
Iron Mountain is a data management company that has a number of clients. For each client, Iron Mountain needs to record the amount of storage consumed on a daily basis. An analyst would like to calculate the average storage consumed by each client on a monthly basis. Can you write a SQL query to solve this problem?
The dataset provided to the analyst looks like this:
Example Input:
| date | client_id | storage_mb |
|---|---|---|
| 01/01/2022 | 1 | 50000 |
| 01/01/2022 | 2 | 60000 |
| 01/02/2022 | 1 | 51000 |
| 01/02/2022 | 2 | 60500 |
| 02/01/2022 | 1 | 52000 |
| 02/01/2022 | 2 | 61000 |
| 02/02/2022 | 1 | 53000 |
| 02/02/2022 | 2 | 61500 |
For example, the average storage consumed by client 1 in January 2022 is (50000 + 51000) / 2 = 50500.
Example Output:
| month | client_id | avg_storage_mb |
|---|---|---|
| January | 1 | 50500 |
| January | 2 | 60250 |
| February | 1 | 52500 |
| February | 2 | 61250 |
Answer:
This query works by grouping the data by both the month and the client_id, then calculating the average storage used for each group. The TO_CHAR(date, 'Month') function is used to extract the month name from the date.
For more window function practice, try this Uber SQL Interview Question within DataLemur's online SQL code editor:
SQL Question 5: What's the difference between a unique 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 Iron Mountain employees:
This index would ensure that no two Iron Mountain 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.
SQL Question 6: Inventory Management Dashboard for Iron Mountain
You are a data analyst at Iron Mountain, a company specializing in records and information management services. One of the tasks is to create a management dashboard that represents the current state of stock in the inventory.
The database has two major tables: and .
The table represents all storage units, their IDs and their maximum capacity.
Example Input:
| unit_id | max_capacity |
|---|---|
| 101 | 1500 |
| 102 | 2500 |
| 103 | 1800 |
| 104 | 2300 |
The table includes all items stored in the units, with their individual weights.
Example Input:
| item_id | unit_id | weight |
|---|---|---|
| 1 | 101 | 500 |
| 2 | 101 | 400 |
| 3 | 102 | 2300 |
| 4 | 103 | 1200 |
| 5 | 103 | 100 |
| 6 | 104 | 1100 |
| 7 | 104 | 1000 |
The task is to create a query that computes the total current weight in each unit, the remaining capacity and a boolean variable that will indicate if the unit is over capacity (True means the unit is over its capacity).
Answer:
This query works by joining the and tables on and then, for each , it sums up the of corresponding items (if there are no items, is used to default the sum to 0). After that, it calculates the remaining capacity by subtracting the current weight from the max capacity and sets the as True if the remaining capacity is negative, which would indicate that a unit is over its maximum capacity.
SQL Question 7: What's the difference between the and window function?
Both the and window functions are used to access a row at a specific offset from the current row.
However, the function retrieves a value from a row that follows the current row, whereas the function retrieves a value from a row that precedes the current row.
Say you had a table of salary data for Iron Mountain employees:
| name | salary |
|---|---|
| Amanda | 130000 |
| Brandon | 90000 |
| Carlita | 80000 |
You could use the function to output the salary of each employee, along with the next highest-paid employee:
This would yield the following output:
| name | salary | next_salary |
|---|---|---|
| Amanda | 130000 | 90000 |
| Brandon | 90000 | 80000 |
| Carlita | 80000 | NULL |
Swapping for would get you the salary of the person who made just more than you:
| name | salary | next_salary |
|---|---|---|
| Amanda | 130000 | NULL |
| Brandon | 90000 | 130000 |
| Carlita | 80000 | 90000 |
SQL Question 8: Filter Customer Records for Iron Mountain
Iron Mountain is a company that specializes in information management and storage solutions. Your task is to write a SQL query that filters the customer records database. Filter for customers that are looking for either 'Global data backup' or 'Cloud storage' services and are located either in 'New York' or 'California'. Also, filter out the customers who are not 'Active'.
Sample Input:
table:
Expected Output:
Answer:
This query uses WHERE clause along with AND and IN keywords to filter the records in the customer table. The SQL IN keyword allows for multiple OR conditions. The query first checks if the service the customer is interested in is either 'Global data backup' or 'Cloud storage'. Then, it checks whether the customer is located in either 'New York' or 'California'. Lastly, it ensures that the status of the customer is 'Active'. All these conditions must be met, hence the use of AND. If the record meets all these conditions, it is returned in the resultset.
Iron Mountain 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.
Besides solving the above Iron Mountain SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like Google, Microsoft and Silicon Valley startups.
Each problem on DataLemur has hints to guide you, detailed solutions and most importantly, there's an online SQL coding environment so you can right in the browser run your query and have it graded.
To prep for the Iron Mountain SQL interview it is also a great idea to solve SQL problems from other telecom and REIT companies like:
However, if your SQL skills are weak, don't worry about jumping right into solving questions – strengthen your SQL foundations with this SQL tutorial for Data Analytics.
This tutorial covers SQL topics like finding NULLs and LEAD/LAG window functions – both of which pop up frequently during Iron Mountain SQL assessments.
Iron Mountain Data Science Interview Tips
What Do Iron Mountain Data Science Interviews Cover?
In addition to SQL interview questions, the other types of problems to practice for the Iron Mountain Data Science Interview include:
- Probability & Stats Questions
- Python or R Programming Questions
- Product & Business Analytics Questions
- Machine Learning Questions
- Behavioral Interview Questions
How To Prepare for Iron Mountain Data Science Interviews?
The best way to prepare for Iron Mountain Data Science interviews is by reading Ace the Data Science Interview. The book's got:
- 201 Interview Questions from FAANG & startups
- A Crash Course on Product Analytics, SQL & ML
- Amazing Reviews (1000+ reviews, 4.5-star rating)