9 Community Health Systems SQL Interview Questions (Updated 2024)
Community Health Systems employees write SQL queries to analyze patient data, helping them identify areas for improvement in patient care and hospital services. They also use SQL to manage large databases, making it easier to retrieve important information quickly and accurately when needed, that is why Community Health Systems asks SQL questions during interviews for Data Science and Data Engineering roles.
So, to help you practice, we've curated 9 Community Health Systems SQL interview questions – can you solve them?
9 Community Health Systems SQL Interview Questions
SQL Question 1: Identify High Frequency Visitors
Community Health Systems operate a vast hospital network. They are interested in tracking high frequency visitors to their health centers. These "VIP Users" are defined as patients who visit the hospital 4 or more times in a month.
Your task involves writing a SQL query that identifies these VIP users using the table.
Example Input:
| visit_id | patient_id | visit_date | center_id |
|---|---|---|---|
| 2051 | 23 | 05/10/2021 | 101 |
| 2655 | 45 | 05/15/2021 | 202 |
| 4782 | 23 | 05/18/2021 | 101 |
| 5352 | 54 | 06/26/2021 | 303 |
| 4517 | 23 | 05/27/2021 | 101 |
| 9886 | 23 | 05/30/2021 | 202 |
Example Output:
| month | year | patient_id | total_visits |
|---|---|---|---|
| 5 | 2021 | 23 | 4 |
Answer:
This PostgreSQL query extracts the month and year from the field and groups the number of visits by , month, and year. The clause is used to filter the groups to only those with a total visit count of 4 or more, identifying the high-frequency "VIP Users."
To solve a similar VIP customer analysis question on DataLemur's free interactive coding environment, try this Microsoft Azure Cloud SQL Interview Question:
Visit Community Health Systems' press room to discover their latest media releases and updates on their healthcare services! Staying informed about CHS can provide insights into how they are working to improve healthcare delivery and patient care across the country.
SQL Question 2: 2nd Largest Salary
Given a table of Community Health Systems employee salary data, write a SQL query to find the 2nd highest salary at the company.
Community Health Systems Example Input:
| employee_id | salary |
|---|---|
| 1 | 2500 |
| 2 | 800 |
| 3 | 1000 |
| 4 | 1200 |
Example Output:
| second_highest_salary |
|---|
| 1200 |
Code your solution to this problem and run your code right in the browser:
Answer:
You can find a detailed solution here: 2nd Highest Salary.
SQL Question 3: What's database denormalization?
Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1NF, 2NF, 3NF, etc.).
This is typically 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.
Denormalization can improve query performance by reducing the number of expensive joins required to retrieve data, but it comes with it's 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: Average Patient Satisfaction Over Time
For Community Health Systems, patient satisfaction is an important KPI. Suppose you're given a dataset of patient satisfaction scores provided after every visit. In a small timeframe like monthly or yearly, the company wants to know the average patient satisfaction to assess their performance.
Here’s a sample table:
Example Input:
| visit_id | patient_id | visit_date | satisfaction_score |
|---|---|---|---|
| 101 | 105 | 01/10/2022 | 8 |
| 102 | 201 | 02/10/2022 | 7 |
| 103 | 105 | 03/04/2022 | 9 |
| 104 | 203 | 02/20/2022 | 6 |
| 105 | 201 | 01/15/2022 | 7 |
| 106 | 202 | 03/12/2022 | 8 |
| 107 | 204 | 01/07/2022 | 9 |
| 108 | 105 | 02/23/2022 | 7 |
| 109 | 205 | 01/30/2022 | 5 |
| 110 | 202 | 02/25/2022 | 8 |
Your task is to write a SQL query to find the average satisfaction score per month for the year of 2022.
Answer:
Here is an example of how you could structure your query using PostgreSQL:
This query works by first extracting the month and year parts of the using the function. The clause ensures we're only looking at data from 2022. Then, we group by the extracted month and calculate the average satisfaction score for each month with the function. The results are ordered by the month for easier readability.
p.s. Window functions show up super frequently during SQL interviews, so practice the 27+ window function questions on DataLemur
SQL Question 5: Why would it make sense to denormalize a database?
Denormalization is the practice of altering a database schema in a way that breaks the normalization rules (1st, 2nd, 3rd normal forms).
Here's 3 reasons to de-normalize a database at Community Health Systems:
-
Improved performance: Denormalization can often improve performance by reducing the number of expensive join operations required to retrieve data. This is particularly useful when the database is being used for online analytical processing (OLAP) as frequent joins across multiple tables can be slow and costly.
-
Scalability: Denormalization can increase the scalability of a database by requiring less data to be read and processed when executing a query. This can be beneficial when the database is expected to handle a high volume of queries.
-
Simplification: One way to simplify the design of a database is by using denormalization to reduce the number of tables and relationships that need to be managed. This can make the database easier to understand and maintain.
SQL Question 6: Filter patient information based on their health history and recent visits
In Community Health Systems, the management wants to have a targeted health approach for patients with chronic conditions like Diabetes or Heart Disease. They want information about patients, who are over 50 years old, have Diabetes or Heart Disease, and haven't visited any of their facilities for over 6 months.
Generate a list of these patients with their last visit's date, to plan for a specialized care program.
Example Input:
| patient_id | name | age | condition |
|---|---|---|---|
| 100 | John Doe | 52 | Diabetes |
| 101 | Jane Doe | 45 | Heart Disease |
| 102 | Jim Brown | 55 | Healthy |
| 103 | Jill White | 60 | Heart Disease |
| 104 | Jack Black | 50 | Diabetes |
Example Input:
| patient_id | visit_date |
|---|---|
| 100 | 2021-01-15 |
| 101 | 2021-07-20 |
| 102 | 2022-03-10 |
| 103 | 2021-12-05 |
| 104 | 2022-03-01 |
Answer:
This query first creates a subquery for the latest visit dates for each patient. It then filters the table on both age and condition records and finally on visits older than 6 months. The result is a list of patients, their condition, and last visit date, who haven't visited any CHS facilities for over 6 months.
SQL Question 7: In database design, what do foreign keys do?
A foreign key is a field in a database table that links to the primary key of another table, establishing a connection between the two tables. For example, let's analyze Community Health Systems' Google Ads campaigns data:
:
| ad_id | campaign_id | keyword | click_count |
|---|---|---|---|
| 1 | 201 | Community Health Systems reviews | 120 |
| 2 | 202 | Community Health Systems pricing | 150 |
| 3 | 101 | buy Community Health Systems | 65 |
| 4 | 101 | Community Health Systems alternatives | 135 |
is a foreign key that connects to the of the corresponding Google Ads campaign. This establishes a relationship between the ads and their campaigns, enabling easy querying to find which ads belong to a specific campaign or which campaigns a specific ad belongs to.
The table may also have multiple foreign keys that reference primary keys in other tables. For example, and foreign keys could be used to link each ad to its ad group and the Google Ads account that the campaigns belong to, respectively.
SQL Question 8: Average Duration of Hospital Stays
Community Health Systems would like to better understand the average duration of hospital stays for its patients. Could you write a SQL query to calculate the average duration of hospital stays, in days, for each type of diagnosis in the year 2022?
Example Input:
| patient_id | admission_date | discharge_date | diagnosis |
|---|---|---|---|
| 101 | 2022-01-01 | 2022-01-10 | Cardiac |
| 203 | 2022-02-05 | 2022-02-10 | Respiratory |
| 305 | 2022-03-10 | 2022-03-15 | Respiratory |
| 407 | 2022-08-01 | 2022-08-05 | Gastrointestinal |
| 509 | 2022-09-01 | 2022-09-07 | Cardiac |
Example Output:
| diagnosis | avg_duration |
|---|---|
| Cardiac | 7.5 |
| Respiratory | 5 |
| Gastrointestinal | 4 |
Answer:
This SQL query first selects the and calculates the duration of the hospital stay by subtracting the from the . We are grouping by to compute the average for each diagnosis. The clause is used to limit the data to only include hospital stays that started in the year 2022.
To practice a very similar question try this interactive Facebook Average Post Hiatus (Part 1) Question which is similar for calculating time difference or this Alibaba Compressed Mean Question which is similar for calculating averages.
SQL Question 9: Locating Specific Patient Data
The Community Health Systems serves patients across hundreds of communities. To better provide individualized services, the patient's records are stored in our database. Our goal in this case is to use SQL to filter the patients who were diagnosed with a condition containing the word "heart" in their patients' records to understand the current landscape of heart-related conditions among our patients.
Example Input:
| patient_id | first_name | last_name | dob | diagnosis |
|---|---|---|---|---|
| 10245 | John | Smith | 01/08/1980 | Heart disease |
| 78962 | Jane | Doe | 12/04/1975 | High blood pressure |
| 44563 | Joe | Johnson | 08/15/1965 | Heart failure |
| 65984 | Ann | Taylor | 20/07/1974 | Diabetes |
| 93867 | Paul | Miller | 06/02/1986 | Atrial fibrillation |
Example Output:
| patient_id | first_name | last_name | diagnosis |
|---|---|---|---|
| 10245 | John | Smith | Heart disease |
| 44563 | Joe | Johnson | Heart failure |
| 93867 | Paul | Miller | Atrial fibrillation |
Answer:
The above query selects the , , , and columns from the table where the diagnosis contains "heart." The '%' before and after 'heart' is a wildcard that matches any sequence of characters, enabling identification of all patients who have been diagnosed with conditions containing the word "heart."
Community Health Systems SQL Interview Tips
Assuming that you've already got basic SQL skills, the next best tip we have to prepare for the Community Health Systems SQL interview is to solve as many practice SQL interview questions as you can! Beyond just solving the above Community Health Systems SQL interview questions, you should also solve the 200+ SQL Interview Questions on DataLemur which come from companies like FAANG (FB, Apple, Amazon, Netflix, Google).
Each exercise has hints to guide you, fully explained answers along with a discussion board to see how others solved it and most importantly, there's an online SQL coding environment so you can right in the browser run your query and have it checked.
To prep for the Community Health Systems SQL interview it is also wise to solve SQL questions from other healthcare and pharmaceutical companies like:
- Henry Schein SQL questions
- Universal Health Services SQL questions
- Baxter International SQL questions
- IQVIA SQL questions
However, if your SQL query skills are weak, forget about jumping right into solving questions – go learn SQL with this free SQL tutorial.
This tutorial covers things like SUM/AVG window functions and using ORDER BY – both of which pop up frequently in SQL interviews at Community Health Systems.
Community Health Systems Data Science Interview Tips
What Do Community Health Systems Data Science Interviews Cover?
In addition to SQL interview questions, the other types of questions tested in the Community Health Systems Data Science Interview include:
- AB Testing & Experimentation Questions
- Python or R Programming Questions
- Product Analytics Questions
- ML Modelling Questions
- Behavioral Questions focussed on Community Health Systems culture and values
How To Prepare for Community Health Systems Data Science Interviews?
To prepare for Community Health Systems Data Science interviews read the book Ace the Data Science Interview because it's got:
- 201 interview questions sourced from tech companies like Google & Microsoft
- a crash course covering SQL, Product-Sense & ML
- over 1000+ 5-star reviews on Amazon
Also focus on the behavioral interview – prepare for it with this guide on behavioral interview questions.