10 Cerner SQL Interview Questions (Updated 2024)
Data Scientists, Analysts, and Data Engineers at Cerner write SQL queries to analyze healthcare data, allowing them to identify trends and improve patient outcomes. They also use SQL to create predictive models that help healthcare providers anticipate patient needs, this is the reason why Cerner evaluates jobseekers on SQL coding interview questions.
As such, to help you study for the Cerner SQL interview, here’s 10 Cerner SQL interview questions – scroll down to start solving them!
10 Cerner SQL Interview Questions
SQL Question 1: Get Each Physician's Average Patient Rating Over Time
You are a data analyst at Cerner and your supervisor asks you to analyze patient satisfaction over time in order to help them understand which physicians are performing well and which may need additional support. You are given the following patient satisfaction survey data:
Example Input:
| survey_id | physician_id | end_date | patient_id | rating |
|---|---|---|---|---|
| 101 | Doc001 | 2021-01-01 | Pat001 | 4 |
| 102 | Doc002 | 2021-01-15 | Pat002 | 5 |
| 103 | Doc001 | 2021-02-01 | Pat003 | 3 |
| 104 | Doc003 | 2021-02-15 | Pat004 | 4 |
| 105 | Doc002 | 2021-03-01 | Pat005 | 2 |
Write a SQL query that returns a running average rating for each physician by month and year.
Answer:
The following script uses the function and the clause to calculate a running average for each physician's patient ratings. This running average is partitioned by physician and calculated for each end_date in ascending order. is used to get the first day of the month for each end_date:
This query uses window functions to calculate a running average, which includes the current row and all preceding rows. This allows us to generate a table that shows how each physician's average patient rating changes over time.
For more window function practice, solve this Uber SQL problem on DataLemur's online SQL code editor:
Stay updated with Cerner's latest news, where technology and innovation intersect to drive business solutions across various industries! Learning about Cerner's advancements can enhance your understanding of how technology is transforming the business landscape.
SQL Question 2: 2nd Highest Salary
Given a table of Cerner employee salary data, write a SQL query to find the 2nd highest salary among all employees.
Cerner Example Input:
| employee_id | salary |
|---|---|
| 1 | 2500 |
| 2 | 800 |
| 3 | 1000 |
| 4 | 1200 |
Example Output:
| second_highest_salary |
|---|
| 1200 |
Write a SQL query for this problem directly within the browser on DataLemur:
Answer:
You can find a detailed solution with hints here: 2nd Highest Salary.
SQL Question 3: What is denormalization?
Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).
Denormalization is done to improve the performance of the database when it is being used for online analytics processing (OLAP), rather than online transaction processing (OLTP) use cases.
For these OLAP use cases, you're bottleneck frequently is joining multiple tables, but de-normalizing your database cuts these outs.
Denormalization can improve query performance by reducing the number of expensive joins required to retrieve data, but it comes with its own drawbacks too. By adding redundant columns, you incur more data storage costs, and there's need for more complex update and delete operations in order to maintain data integrity across all the duplicated data. Thus, it's important to carefully consider the trade-offs involved before implementing denormalization.
SQL Question 4: Healthcare Provider Database Design
Cerner is a supplier of health information technology solutions thus, let's design a database for a simple model of their service. We have healthcare providers (doctors) and patients. Each patient has one primary care provider. A healthcare provider can have multiple patients. Each patient has multiple appointments with their healthcare provider, and the results of each appointment are recorded. How would you model this in SQL?
Can you write a query that returns the name of the healthcare provider who has the most appointments?
Example Input:
| provider_id | name |
|---|---|
| 1 | Dr. Smith |
| 2 | Dr. Johnson |
| 3 | Dr. Taylor |
Example Input:
| patient_id | name | provider_id |
|---|---|---|
| 101 | Alice | 1 |
| 102 | Bob | 3 |
| 103 | Charlie | 2 |
| 104 | David | 1 |
| 105 | Erin | 2 |
Example Input:
| appointment_id | patient_id | date | results |
|---|---|---|---|
| 9001 | 101 | 06/08/2022 | Positive |
| 9002 | 101 | 06/12/2022 | Positive |
| 9003 | 102 | 06/15/2022 | Negative |
| 9004 | 103 | 06/18/2022 | Positive |
| 9005 | 104 | 07/05/2022 | Negative |
| 9006 | 105 | 07/15/2022 | Negative |
| 9007 | 105 | 07/20/2022 | Positive |
Answer:
This query joins the , , and tables to count the number of appointments each provider has had, it then orders the list in descending number of appointments and returns the provider with the most appointments.
SQL Question 5: Can you explain the purpose of UNION?
In SQL, the operator combines the result of two or more SELECT statements into a single result set. Note that each statement within the UNION must have the same number of columns and the columns must have similar data types. The operator removes duplicates from the final result set. If you want to include duplicates in the final result set, you can use the operator instead.
Here's an example of using the operator to combine the results of two statements that retrieve data from tables of Cerner's Facebook ads and their Google ads:
This statement would return a combined result set of both Facebook and Google ads that have a spend greater than $500.
SQL Question 6: Filter Patients Information Based on Hospital Records
Given a hospital database that contains patient records and associated hospitals. Write an SQL query to filter all the patients who were admitted to the 'Cerner General Hospital' and diagnosed with 'Cardiovascular Disease'. Also include patients from 'Cerner Children's Hospital' diagnosed with 'Cancer' in your result set.
Example Input:
| patient_id | name | admit_date | hospital_id | disease |
|---|---|---|---|---|
| 1234 | John Doe | 07/10/2022 00:00:00 | 011 | Cardiovascular Disease |
| 2345 | Jane Doe | 07/15/2022 00:00:00 | 022 | Cancer |
| 3456 | Sam Smith | 07/18/2022 00:00:00 | 011 | Diabetes |
| 4567 | Emily Johnson | 07/20/2022 00:00:00 | 022 | Cardiovascular Disease |
| 5678 | Robert Brown | 07/25/2022 00:00:00 | 011 | Cancer |
Example Input:
| hospital_id | name |
|---|---|
| 011 | Cerner General Hospital |
| 022 | Cerner Children's Hospital |
Example Output:
| patient_id | name | admit_date | hospital | disease |
|---|---|---|---|---|
| 1234 | John Doe | 07/10/2022 00:00:00 | Cerner General Hospital | Cardiovascular Disease |
| 2345 | Jane Doe | 07/15/2022 00:00:00 | Cerner Children's Hospital | Cancer |
| 5678 | Robert Brown | 07/25/2022 00:00:00 | Cerner General Hospital | Cancer |
Answer:
This query joins and tables on and filters patients who have either 'Cardiovascular Disease' and admitted to 'Cerner General Hospital' or have 'Cancer' and admitted to 'Cerner Children's Hospital'. The clause includes multiple boolean conditions combined with , keywords that filter data based on the hospital and disease.
SQL Question 7: Can you describe the difference between a correlated and a non-correlated sub-query?
A correlated sub-query is one that relies on the outer query and cannot be run independently. It uses the outer query to filter or transform data by referencing a column from it, while the outer query uses the results of the inner query. On the other hand, a non-correlated sub-query is not linked to the outer query and can be run on its own. It does not reference any columns from the outer query and is used to retrieve additional data for the outer query.
An example correlated sub-query:
This correlated subquery retrieves the names and salaries of Cerner employees who make more than the average salary for their department. The subquery references the department column in the main query's clause () and uses it to filter the rows of the subquery's clause ().
An example non-correlated sub-query:
This non-correlated subquery retrieves the names and salaries of Cerner employees who make more than the average salary for the Data Analytics department (which honestly should be very few people since Data Analysts are awesome).
Anyways, the subquery is independent of the main query and can be considered a standalone query. Its output (the average salary for the Data Analytics department) is then used in the main query to filter the rows of the table.
SQL Question 8: Calculating Click Through Rates for Cerner's Digital Products
As part of Cerner's digital product line, we have numerous healthcare software solutions. Each of these products has a specific landing page, and we run ads directing potential customers to them. We track the number of times an ad was shown (), the number of times an ad was clicked (), and the number of times a viewed product was added to the user's cart ().
We want you to calculate the Click-Through Rate (CTR) and the Conversion Rate (CR), defined as follows:
CTR = (Number of Clicks / Number of Impressions) * 100 CR = (Number of Adds to Cart / Number of Clicks) * 100
for each product.
For simplicity, assume you have the following two tables:
Example Input:
| product_id | impressions | clicks |
|---|---|---|
| 101 | 1000 | 50 |
| 102 | 2000 | 150 |
| 103 | 500 | 10 |
| 104 | 3000 | 100 |
| 105 | 1200 | 60 |
Example Input:
| product_id | add_to_cart |
|---|---|
| 101 | 5 |
| 102 | 45 |
| 103 | 1 |
| 104 | 10 |
| 105 | 20 |
Answer:
This SQL command calculates the required rates by joining the table and the table on the column. It then calculates the CTR and CR for each product and returns these alongside the .
To solve a related SQL interview question on DataLemur's free online SQL code editor, attempt this Meta SQL interview question:
SQL Question 9: Filtering Patient Records by Name Pattern
Cerner Corporation is a supplier of health information technology solutions, services, devices, and hardware. Let's assume that as a Cerner employee, you typically work with the patient records database. A common task you may be asked to perform is to filter down the patient records by surname, using the SQL keyword to find records that match a specific pattern or string.
Sample Table Input:
| patient_id | first_name | last_name | date_of_birth | diagnosis |
|---|---|---|---|---|
| 101 | John | Doe | 1990-03-21 | Diabetes |
| 102 | Jane | Smith | 1976-07-14 | Hypertension |
| 103 | Michael | Johnson | 1985-11-11 | Asthma |
| 104 | Sara | Doe | 2001-01-31 | Diabetes |
| 105 | David | Dawson | 1992-09-15 | None |
The question is: Write a SQL command to list out all patients whose last name starts with 'D'.
Answer:
This query uses the keyword, combined with the wildcard character, to filter for all records in the table where the field begins with 'D'. The character means "match any substring," so 'D%' will match any string that begins with 'D'.
SQL Question 10: Consider unique indexes, and non-unique indexes. What are some similarities and differences?
Unique indexes help ensure that there are no duplicate key values in a table, maintaining data integrity. They enforce uniqueness whenever keys are added or changed within the index.
To define a unique index in PostgreSQL, you can use the following syntax:
To define a non-unique index in PostgreSQL, you can use the following syntax:
Non-unique indexes on the other hand, are used to improve query performance by maintaining a sorted order of frequently used data values, but they do not enforce constraints on the associated table.
Preparing For The Cerner SQL Interview
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 above Cerner SQL interview questions, you should also solve the 200+ DataLemur SQL Interview Questions which come from companies like Meta, Google and healthcare and pharmaceutical companies like Cerner.
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 coding environment so you can right online code up your SQL query and have it executed.
To prep for the Cerner SQL interview it is also a great idea to practice interview questions from other healthcare and pharmaceutical companies like:
- Patterson SQL questions
- Select Medical Holdings SQL questions
- Vertex Pharmaceuticals SQL questions
- Zoetis SQL questions
However, if your SQL skills are weak, don't worry about diving straight into solving questions – refresh your SQL knowledge with this DataLemur SQL tutorial.
This tutorial covers SQL topics like using LIKE and turning a subquery into a CTE – both of these pop up routinely in Cerner SQL interviews.
Cerner Data Science Interview Tips
What Do Cerner Data Science Interviews Cover?
Beyond writing SQL queries, the other types of questions to prepare for the Cerner Data Science Interview include:
- Probability & Stats Questions
- Python Pandas or R Coding Questions
- Product Data Science Interview Questions
- Machine Learning Questions
- Behavioral Questions based on Cerner company values
How To Prepare for Cerner Data Science Interviews?
To prepare for Cerner Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions taken from FAANG, tech startups, and Wall Street
- a refresher on Python, SQL & ML
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Don't ignore the behavioral interview – prep for it using this guide on acing behavioral interviews.