11 HCA Healthcare SQL Interview Questions (Updated 2024)
At HCA Healthcare, they use SQL to analyze patient records for trends, helping them identify patterns that can improve patient care and outcomes. They also use SQL to manage large databases of medical information, allowing for efficient access to critical data when making healthcare decisions, that is the reason why HCA Healthcare asks SQL questions during interviews for Data Science, Data Engineering, and Data Analytics positions.
Thus, to help you ace the HCA Healthcare SQL interview, we've curated 11 HCA Healthcare SQL interview questions in this article.
11 HCA Healthcare SQL Interview Questions
SQL Question 1: Identifying Frequent Users of HCA Healthcare
For HCA Healthcare, a possible analysis could be to determine patients who have had the most number of healthcare visits in the last year. These could be considered as the 'VIP' or 'whale' customers for the firm. Also, these frequent visits could be indicative of chronic health conditions, which is valuable information for HCA Healthcare.
So the SQL question could be: Given two tables - Patients and Visits, write a SQL query to identify the top 5 patients who had the maximum number of visits in the last year.
Example Input:
| patient_id | first_name | last_name | dob |
|---|---|---|---|
| 1 | John | Doe | 01/01/1980 |
| 2 | Jane | Smith | 02/02/1982 |
| 3 | Harry | Potter | 31/07/1980 |
| 4 | Luna | Lovegood | 13/02/1981 |
| 5 | Hermione | Granger | 19/09/1979 |
Example Input:
| visit_id | patient_id | visit_date |
|---|---|---|
| 101 | 1 | 20/11/2021 |
| 102 | 2 | 13/02/2022 |
| 103 | 3 | 30/01/2022 |
| 104 | 4 | 07/03/2022 |
| 105 | 1 | 23/03/2022 |
| 106 | 1 | 14/05/2022 |
| 107 | 2 | 06/04/2022 |
| 108 | 5 | 18/05/2022 |
Answer:
This SQL query first joins the table with the table on the column. It then restricts the data to only include visits from the last one year. It then counts the number of visits per patient (by grouping by ), orders these counts in descending order, and returns the top 5 patients with the maximum number of visits along with their names.
To practice a related customer analytics question on DataLemur's free interactive coding environment, try this Microsoft Azure Cloud SQL Interview Question:
Explore HCA Healthcare's news to stay updated on their latest developments and strategic initiatives in the healthcare sector! Understanding HCA's progress can provide valuable insights into how they are enhancing patient care and expanding their services.
SQL Question 2: Department Salaries
Imagine you had a table of HCA Healthcare employee salary data, along with which department they belonged to. Write a query to compare the average salary of employees in each department to the company's average salary for March 2024. Return the comparison result as 'higher', 'lower', or 'same' for each department. Display the department ID, payment month (in MM-YYYY format), and the comparison.
You can solve this problem directly within the browser on DataLemur:
The answer is LONG – 30+ lines of SQL. You can find a step-by-step solution here: Department vs. Company Salary.
SQL Question 3: What does do, and when would you use this function?
The function accepts an unlimited number of input arguments, and returns the first argument from that list which isn't null.If all input arguments are null, will return null too.
For example, suppose you had data on HCA Healthcare salespeople, and the amount of deals they closed. This data was exported from a 3rd-party system CRM, which exports a value if the salesperson didn't close any deals.
| sales_person | closed_deals |
|---|---|
| Jason Wright | 4 |
| Drew Jackson | NULL |
| Chris Ho | 2 |
| Adam Cohen | NULL |
| Samantha Perez | 3 |
To get rid of these NULLs, and replace them with zero's (so you can do some further analytics like find the average number of closed deals), you would use the function as follows:
You'd get the following output:
| sales_person | closed_deals |
|---|---|
| Jason Wright | 4 |
| Drew Jackson | 0 |
| Chris Ho | 2 |
| Adam Cohen | 0 |
| Samantha Perez | 3 |
SQL Question 4: Analyze Patients Visit Data
You are given a dataset of patient visits at HCA Healthcare. Each row represents a single visit by a patient, identified by , to a particular department, identified by . Each visit also has an associated date () and a score given by the patient about his/her experience in the visit ().
The score ranges from 1 to 10, where 10 represents the best possible experience.
You are asked to write a SQL query to find out the average score of each department for each calendar month, as well as the ranking of score within each calendar month.
Example Input:
| visit_id | patient_id | department_id | visit_date | score |
|---|---|---|---|---|
| 1 | 1 | 1 | 2022-06-15 | 9 |
| 2 | 2 | 1 | 2022-06-10 | 7 |
| 3 | 3 | 1 | 2022-07-25 | 6 |
| 4 | 4 | 2 | 2022-06-01 | 8 |
| 5 | 5 | 2 | 2022-07-20 | 10 |
Answer:
This SQL query first calculates the average score for each department for each month. It then uses a window function () to rank the departments within each month based on their average scores. The clause helps to restart the ranking for each month.
To solve a related window function SQL problem on DataLemur's free online SQL code editor, solve this Amazon SQL Interview Question:
SQL Question 5: What does / SQL commands do?
The / operator is used to remove to return all rows from the first statement that are not returned by the second statement.
Note that is available in PostgreSQL and SQL Server, while is available in MySQL and Oracle (but don't stress about knowing which DBMS supports what exact commands since the interviewers at HCA Healthcare should be lenient!).
For a tangible example in PostgreSQL, suppose you were doing an HR Analytics project for HCA Healthcare, and had access to HCA Healthcare'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:
SQL Question 6: Analyze Patient Visit Trends Over Certain Illnesses in HCA Healthcare
Assume HCA Healthcare has a system where they maintain records of all patient visits, and each visit has details like who the patient is, what illness was the reason for their visit, the date of the visit, the doctor who attended them and the hospital it took place.
They would like a SQL query to provide an overview of the top 3 illnesses which had the most patient visits per month over the past year, for quality improvement purposes in handling these common cases.
Example Input:
| visit_id | patient_id | visit_date | illness_id | doctor_id | hospital_id |
|---|---|---|---|---|---|
| 1001 | 2001 | 01/10/2022 00:00:00 | 3001 | 4001 | 5001 |
| 1002 | 2002 | 01/15/2022 00:00:00 | 3002 | 4002 | 5002 |
| 1003 | 2003 | 01/20/2022 00:00:00 | 3001 | 4003 | 5003 |
| 1004 | 2004 | 02/05/2022 00:00:00 | 3001 | 4004 | 5004 |
| 1005 | 2005 | 02/10/2022 00:00:00 | 3003 | 4005 | 5005 |
| 1006 | 2006 | 02/15/2022 00:00:00 | 3002 | 4006 | 5006 |
Example Output:
| month | illness_id | total_visits |
|---|---|---|
| 1 | 3001 | 2 |
| 1 | 3002 | 1 |
| 2 | 3001 | 1 |
| 2 | 3002 | 1 |
| 2 | 3003 | 1 |
Example PostgreSQL Query & Explanation:
The question has asked for a total count of visits per illness per month. We can get this information from a simple query where we'll the and the month extracted from the , then we'll the total number of visits in descending order to see the highest counts first.
In this query, the function is used to get the month from the . The clause ensures we're only considering visits from the past year. The clause groups the results by month and . The function counts the number of rows in each group. Finally, the clause sorts the results in descending order by .
SQL Question 7: What does do in a SQL query?
In SQL, the operator combines the result of two or more 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 HCA Healthcare'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 8: Average Duration of Patient's Stay
HCA Healthcare is a provider of health care services. They might ask you to find the average duration of a patient's stay in their hospitals. The task is to find the average number of days a patient stays within a given period using the function.
Consider the table which records patient's hospital stay:
Example Input:
| stay_id | patient_id | admission_date | discharge_date |
|---|---|---|---|
| 201 | 123 | 05/01/2022 | 05/05/2022 |
| 202 | 265 | 05/10/2022 | 05/15/2022 |
| 203 | 362 | 05/11/2022 | 05/20/2022 |
| 204 | 192 | 06/12/2022 | 06/13/2022 |
| 205 | 981 | 06/15/2022 | 06/21/2022 |
Your task is to provide the average patient stay durations for May and June, assuming today's date is 30th June 2022.
Example Output:
| month | avg_stay_duration |
|---|---|
| 5 | 9.33 |
| 6 | 3.50 |
Answer:
This query firstly extracts the month from the admission date and groups by this month. It calculates the duration of each stay by using the function, which returns the duration between two dates. The duration is then extracted in days. Lastly, the average duration of stay for each month is calculated using function.
To practice a very similar question try this interactive Google Median Google Search Frequency Question which is similar for its use of date duration and average calculations or this Facebook Average Post Hiatus (Part 1) Question which is similar for its concept of calculating duration between two events.
SQL Question 9: Analyze Click-Through Rates of Digital Health Services Ads
HCA Healthcare, a healthcare provider, runs a multitude of digital marketing campaigns promoting their various health services. Two key actions measured are views of the ad (or impressions) and clicks on the ad, which leads the user to their website for potential conversion (like setting an appointment).
The marketing team would like to evaluate the performance of these campaigns in terms of the click-through-rate (CTR) which is calculated as the total number of clicks that an ad receives divided by the total number of impressions (clicks/impressions).
Using the table , please provide the CTR for each marketing campaign they have run over the past month.
Example Input:
| ad_id | campaign_id | impressions | clicks |
|---|---|---|---|
| 101 | 1 | 20000 | 250 |
| 102 | 1 | 15000 | 200 |
| 103 | 2 | 18000 | 220 |
| 104 | 2 | 25000 | 500 |
| 105 | 3 | 22000 | 650 |
Desired Output:
| campaign_id | CTR |
|---|---|
| 1 | 0.02 |
| 2 | 0.03 |
| 3 | 0.03 |
Answer:
You can calculate the CTR per campaign by summing the total clicks and impressions for each campaign and then dividing the two. Here's the PostgreSQL query:
This query groups the ads by the and calculates the sum of and for each. It then divides these sums to calculate the CTR. Each campaign's CTR is listed in the output.
To practice a similar problem about calculating rates, try this TikTok SQL Interview Question on DataLemur's online SQL coding environment:
SQL Question 10: What does database normalization mean?
Normalization involves dividing a large table into smaller, more specific ones and establishing connections between them. This helps to reduce redundancy, creating a database that is more adaptable, scalable, and easy to manage. Additionally, normalization helps to maintain the integrity of the data by minimizing the risk of inconsistencies and anomalies.
SQL Question 11: Average number of patients for each department per month.
Given the tables and , find out the average number of patients handled by each department per month.
The table holds data about patient visits, including , , , and .
The table includes and .
Example Input:
| visit_id | patient_id | visit_date | department_id |
|---|---|---|---|
| 5123 | 001 | 06/08/2022 | 100 |
| 4326 | 002 | 06/10/2022 | 200 |
| 2968 | 003 | 06/12/2022 | 100 |
| 1835 | 004 | 07/14/2022 | 200 |
| 7485 | 005 | 07/16/2022 | 100 |
Example Input:
| department_id | department_name |
|---|---|
| 100 | Cardiology |
| 200 | Neurology |
Example Output:
| month | department | avg_patients |
|---|---|---|
| 6 | Cardiology | 2 |
| 6 | Neurology | 1 |
| 7 | Cardiology | 1 |
| 7 | Neurology | 1 |
Answer:
This PostgreSQL query uses the function to get the month from the . It uses to include all the patient logs and matches them with the respective department based on . Aggregate function is used to get the total number of patients and is used to get the total number of days for each month. Dividing total patients by total days gives the average patients per day. The clause groups the result by month and department and sorts the result by month and department.
HCA Healthcare SQL Interview Tips
The best way to prepare for a HCA Healthcare SQL interview is to practice, practice, practice. In addition to solving the earlier HCA Healthcare 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 interview question has multiple hints, step-by-step solutions and crucially, there is an online SQL code editor so you can right online code up your query and have it graded.
To prep for the HCA Healthcare SQL interview it is also wise to solve interview questions from other healthcare and pharmaceutical companies like:
In case your SQL query skills are weak, forget about diving straight into solving questions – refresh your SQL knowledge with this DataLemur SQL tutorial.
This tutorial covers topics including joining a table to itself and aggregate functions – both of which show up frequently in SQL interviews at HCA Healthcare.
HCA Healthcare Data Science Interview Tips
What Do HCA Healthcare Data Science Interviews Cover?
In addition to SQL interview questions, the other topics to prepare for the HCA Healthcare Data Science Interview include:
- Probability & Stats Questions
- Python or R Programming Questions
- Business Sense and Product-Sense Questions
- ML Modelling Questions
- Behavioral Questions focussed on HCA Healthcare cultural values
How To Prepare for HCA Healthcare Data Science Interviews?
To prepare for HCA Healthcare Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions taken from Microsoft, Amazon & startups
- a refresher on Stats, SQL & ML
- over 1000+ 5-star reviews on Amazon
Don't ignore the behavioral interview – prepare for it with this guide on acing behavioral interviews.