๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the employees who joined in the last 30 days.
Assume the table structure:
employees(employee_id, employee_name, department, joining_date)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
employee_id,
employee_name,
department,
joining_date
FROM employees
WHERE joining_date >= CURRENT_DATE - INTERVAL '30 days';
๐ก Explanation:
This query filters employees whose joining date falls within the last 30 days.
โข CURRENT_DATE returns today's date.
โข INTERVAL '30 days' subtracts 30 days from the current date.
โข The WHERE clause returns employees who joined on or after that date.
This question tests your understanding of:
โ Date Functions
โ Date Arithmetic
โ Filtering Records with Dates
๐ฏ Expected Output Example
Employee Department Joining Date
John IT 2026-06-10
Sarah HR 2026-06-22
๐ Database-Specific Alternatives
MySQL
SELECT *
FROM employees
WHERE joining_date >= CURDATE() - INTERVAL 30 DAY;
SQL Server
SELECT *
FROM employees
WHERE joining_date >= DATEADD(DAY, -30, GETDATE());
Oracle
SELECT *
FROM employees
WHERE joining_date >= SYSDATE - 30;
๐ Tip for SQL Job Seekers:
Date-related SQL questions are very common. Make sure you're comfortable with:
โข Finding records from the last N days
โข Current month/year filters
โข Date differences
โข Date formatting
โข Database-specific date functions
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the employees who joined in the last 30 days.
Assume the table structure:
employees(employee_id, employee_name, department, joining_date)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
employee_id,
employee_name,
department,
joining_date
FROM employees
WHERE joining_date >= CURRENT_DATE - INTERVAL '30 days';
๐ก Explanation:
This query filters employees whose joining date falls within the last 30 days.
โข CURRENT_DATE returns today's date.
โข INTERVAL '30 days' subtracts 30 days from the current date.
โข The WHERE clause returns employees who joined on or after that date.
This question tests your understanding of:
โ Date Functions
โ Date Arithmetic
โ Filtering Records with Dates
๐ฏ Expected Output Example
Employee Department Joining Date
John IT 2026-06-10
Sarah HR 2026-06-22
๐ Database-Specific Alternatives
MySQL
SELECT *
FROM employees
WHERE joining_date >= CURDATE() - INTERVAL 30 DAY;
SQL Server
SELECT *
FROM employees
WHERE joining_date >= DATEADD(DAY, -30, GETDATE());
Oracle
SELECT *
FROM employees
WHERE joining_date >= SYSDATE - 30;
๐ Tip for SQL Job Seekers:
Date-related SQL questions are very common. Make sure you're comfortable with:
โข Finding records from the last N days
โข Current month/year filters
โข Date differences
โข Date formatting
โข Database-specific date functions
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค19
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the customer(s) who placed the highest number of orders.
Tables:
customers(customer_id, customer_name)
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
๐ก Explanation:
The query first counts the total number of orders placed by each customer and then ranks them based on the order count.
โ
โ
โ
โ The outer query returns all customers with
This question tests your understanding of:
โ JOIN
โ GROUP BY
โ Aggregate Functions COUNT
โ Window Functions DENSE_RANK
๐ฏ Expected Output Example
Both customers are returned because they are tied for the highest number of orders.
๐ Tip for SQL Job Seekers:
Whenever an interview asks for the highest, lowest, most, or least, think about whether multiple records could tie for first place. Using
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the customer(s) who placed the highest number of orders.
Tables:
customers(customer_id, customer_name)
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
customer_id,
customer_name,
total_orders
FROM (
SELECT
c.customer_id,
c.customer_name,
COUNT(o.order_id) AS total_orders,
DENSE_RANK() OVER (
ORDER BY COUNT(o.order_id) DESC
) AS rnk
FROM customers c
JOIN orders o
ON c.customer_id = o.customer_id
GROUP BY
c.customer_id,
c.customer_name
) ranked
WHERE rnk = 1;
๐ก Explanation:
The query first counts the total number of orders placed by each customer and then ranks them based on the order count.
โ
COUNT(o.order_id) calculates the number of orders per customer.โ
GROUP BY ensures one row per customer.โ
DENSE_RANK() ranks customers from highest to lowest order count.โ The outer query returns all customers with
rnk = 1, including ties.This question tests your understanding of:
โ JOIN
โ GROUP BY
โ Aggregate Functions COUNT
โ Window Functions DENSE_RANK
๐ฏ Expected Output Example
+----------+--------------+
| Customer | Total Orders |
+----------+--------------+
| John | 25 |
| Sarah | 25 |
+----------+--------------+
Both customers are returned because they are tied for the highest number of orders.
๐ Tip for SQL Job Seekers:
Whenever an interview asks for the highest, lowest, most, or least, think about whether multiple records could tie for first place. Using
DENSE_RANK() instead of LIMIT 1 makes your solution more robust and interview-ready.โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค18
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find all employees who have the same manager.
Assume the table structure:
employees(employee_id, employee_name, manager_id)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
e.employee_id,
e.employee_name,
e.manager_id,
m.employee_name AS manager_name
FROM employees e
JOIN employees m
ON e.manager_id = m.employee_id
WHERE e.manager_id IN (
SELECT manager_id
FROM employees
WHERE manager_id IS NOT NULL
GROUP BY manager_id
HAVING COUNT(*) > 1
)
ORDER BY e.manager_id, e.employee_name;
๐ก Explanation:
This query identifies managers who supervise more than one employee and returns all employees reporting to those managers.
โ The subquery groups records by manager_id.
โ HAVING COUNT(*) > 1 finds managers with multiple direct reports.
โ A self join retrieves the manager's name.
โ The outer query returns every employee reporting to those managers.
This question tests your understanding of:
โ Self Joins
โ GROUP BY and HAVING
โ Subqueries
โ Organizational Hierarchies
๐ฏ Expected Output Example
Employee Manager
John David
Alice David
Sarah Michael
Bob Michael
๐ Alternative Using Window Functions
SELECT
employee_id,
employee_name,
manager_id
FROM (
SELECT
*,
COUNT(*) OVER (
PARTITION BY manager_id
) AS team_size
FROM employees
WHERE manager_id IS NOT NULL
) t
WHERE team_size > 1;
This approach uses a window function to count the number of employees under each manager without using GROUP BY.
๐ Tip for SQL Job Seekers:
Hierarchy-based questions are very common in interviews. Practice problems involving:
Employees and managers
Parent-child relationships
Organizational charts
Category trees
Recursive queries WITH RECURSIVE or recursive CTEs
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find all employees who have the same manager.
Assume the table structure:
employees(employee_id, employee_name, manager_id)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
e.employee_id,
e.employee_name,
e.manager_id,
m.employee_name AS manager_name
FROM employees e
JOIN employees m
ON e.manager_id = m.employee_id
WHERE e.manager_id IN (
SELECT manager_id
FROM employees
WHERE manager_id IS NOT NULL
GROUP BY manager_id
HAVING COUNT(*) > 1
)
ORDER BY e.manager_id, e.employee_name;
๐ก Explanation:
This query identifies managers who supervise more than one employee and returns all employees reporting to those managers.
โ The subquery groups records by manager_id.
โ HAVING COUNT(*) > 1 finds managers with multiple direct reports.
โ A self join retrieves the manager's name.
โ The outer query returns every employee reporting to those managers.
This question tests your understanding of:
โ Self Joins
โ GROUP BY and HAVING
โ Subqueries
โ Organizational Hierarchies
๐ฏ Expected Output Example
Employee Manager
John David
Alice David
Sarah Michael
Bob Michael
๐ Alternative Using Window Functions
SELECT
employee_id,
employee_name,
manager_id
FROM (
SELECT
*,
COUNT(*) OVER (
PARTITION BY manager_id
) AS team_size
FROM employees
WHERE manager_id IS NOT NULL
) t
WHERE team_size > 1;
This approach uses a window function to count the number of employees under each manager without using GROUP BY.
๐ Tip for SQL Job Seekers:
Hierarchy-based questions are very common in interviews. Practice problems involving:
Employees and managers
Parent-child relationships
Organizational charts
Category trees
Recursive queries WITH RECURSIVE or recursive CTEs
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค15
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๐ Keyword research: by topic, by your app's languages, from App Store suggestions, by competitors, and with AI analysis.
โข Rankings by country โ history, charts, demand score (0โ100)
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๐ Keyword research: by topic, by your app's languages, from App Store suggestions, by competitors, and with AI analysis.
โข Rankings by country โ history, charts, demand score (0โ100)
โข Global search across any App Store storefront
โข ASO assistant builds your listing for each locale
โข App Store top charts for any country
๐ 14 days of Pro, free ๐ (no card required)
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โค5
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โค4
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the departments where the average salary is greater than the company's overall average salary.
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
department,
AVG(salary) AS average_salary
FROM employees
GROUP BY department
HAVING AVG(salary) > (
SELECT AVG(salary)
FROM employees
);
๐ก Explanation:
The query compares each department's average salary with the company's overall average salary.
โข GROUP BY department calculates the average salary for each department.
โข The subquery computes the overall average salary across all employees.
โข HAVING filters only those departments whose average salary exceeds the company average.
This question tests your understanding of:
โ GROUP BY
โ HAVING
โ Aggregate Functions AVG
โ Subqueries
๐ฏ Expected Output Example
Department: Average Salary
IT: 88,500
Finance: 84,000
HR is excluded because its average salary is below the company average.
๐ Alternative Using a Common Table Expression CTE
WITH company_avg AS (
SELECT AVG(salary) AS avg_salary
FROM employees
)
SELECT
department,
AVG(salary) AS average_salary
FROM employees, company_avg
GROUP BY department, company_avg.avg_salary
HAVING AVG(salary) > company_avg.avg_salary;
Using a CTE can improve readability, especially when the same calculated value is reused in larger queries.
๐ Tip for SQL Job Seekers:
Interviewers often ask questions that compare group-level aggregates with overall aggregates. Master the use of HAVING with subqueriesโitโs a key SQL pattern.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the departments where the average salary is greater than the company's overall average salary.
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
department,
AVG(salary) AS average_salary
FROM employees
GROUP BY department
HAVING AVG(salary) > (
SELECT AVG(salary)
FROM employees
);
๐ก Explanation:
The query compares each department's average salary with the company's overall average salary.
โข GROUP BY department calculates the average salary for each department.
โข The subquery computes the overall average salary across all employees.
โข HAVING filters only those departments whose average salary exceeds the company average.
This question tests your understanding of:
โ GROUP BY
โ HAVING
โ Aggregate Functions AVG
โ Subqueries
๐ฏ Expected Output Example
Department: Average Salary
IT: 88,500
Finance: 84,000
HR is excluded because its average salary is below the company average.
๐ Alternative Using a Common Table Expression CTE
WITH company_avg AS (
SELECT AVG(salary) AS avg_salary
FROM employees
)
SELECT
department,
AVG(salary) AS average_salary
FROM employees, company_avg
GROUP BY department, company_avg.avg_salary
HAVING AVG(salary) > company_avg.avg_salary;
Using a CTE can improve readability, especially when the same calculated value is reused in larger queries.
๐ Tip for SQL Job Seekers:
Interviewers often ask questions that compare group-level aggregates with overall aggregates. Master the use of HAVING with subqueriesโitโs a key SQL pattern.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค12
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โค3
Want to become a pro in Data Analytics and crack interviews?
Focus on these key topics: ๐
1) Understand Data Analytics basics & tools
2) Learn Excel for data cleaning & analysis
3) Master SQL for data querying
4) Study data visualization principles
5) Get hands-on with Power BI/Tableau dashboards
6) Explore statistics & probability fundamentals
7) Learn data wrangling and preprocessing
8) Understand data storytelling and report writing
9) Practice hypothesis testing & A/B testing
10) Get familiar with Python/R for analytics (optional but helpful)
11) Work on real datasets and case studies (Kaggle is great)
12) Build end-to-end projects from data collection to visualization
13) Learn how to communicate insights effectively
14) Practice problem-solving with datasets regularly
15) Optimize your resume with analytics keywords
16) Follow analytics experts and tutorials on YouTube/LinkedIn
Pro tip: Search each topic on YouTube and watch short 10-15 min videos. Practice alongside to build strong fundamentals.
17) Finally, watch full data analytics project walkthroughs and try them yourself.
18) Learn integration of SQL and Power BI/Tableau for advanced reporting.
Credits: https://t.me/sqlspecialist
React โค๏ธ for more
Focus on these key topics: ๐
1) Understand Data Analytics basics & tools
2) Learn Excel for data cleaning & analysis
3) Master SQL for data querying
4) Study data visualization principles
5) Get hands-on with Power BI/Tableau dashboards
6) Explore statistics & probability fundamentals
7) Learn data wrangling and preprocessing
8) Understand data storytelling and report writing
9) Practice hypothesis testing & A/B testing
10) Get familiar with Python/R for analytics (optional but helpful)
11) Work on real datasets and case studies (Kaggle is great)
12) Build end-to-end projects from data collection to visualization
13) Learn how to communicate insights effectively
14) Practice problem-solving with datasets regularly
15) Optimize your resume with analytics keywords
16) Follow analytics experts and tutorials on YouTube/LinkedIn
Pro tip: Search each topic on YouTube and watch short 10-15 min videos. Practice alongside to build strong fundamentals.
17) Finally, watch full data analytics project walkthroughs and try them yourself.
18) Learn integration of SQL and Power BI/Tableau for advanced reporting.
Credits: https://t.me/sqlspecialist
React โค๏ธ for more
โค17
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โค2
I see so many people jump into data analytics, excited by its popularity, only to feel lost or uninterested soon after. I get it, data isnโt for everyone, and thatโs okay.
Data analytics requires a certain spark or say curiosity. You need that drive to dig deeper, to understand why things happen, to explore how data pieces connect to reveal a bigger picture. Without that spark, itโs easy to feel overwhelmed or even bored.
Before diving in, ask yourself, Do I really enjoy solving puzzles? Am I genuinely excited about numbers, patterns, and insights? If youโre curious and love learning, data can be incredibly rewarding. But if itโs just about following a trend, it might not be a fulfilling path for you.
Be honest with yourself. Find your passion, whether itโs in data or somewhere else and invest in something that truly excites you.
Hope this helps you ๐
Data analytics requires a certain spark or say curiosity. You need that drive to dig deeper, to understand why things happen, to explore how data pieces connect to reveal a bigger picture. Without that spark, itโs easy to feel overwhelmed or even bored.
Before diving in, ask yourself, Do I really enjoy solving puzzles? Am I genuinely excited about numbers, patterns, and insights? If youโre curious and love learning, data can be incredibly rewarding. But if itโs just about following a trend, it might not be a fulfilling path for you.
Be honest with yourself. Find your passion, whether itโs in data or somewhere else and invest in something that truly excites you.
Hope this helps you ๐
โค25
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the month with the highest total sales.
Assume the table structure: sales(sale_id, sale_date, amount)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
EXTRACT(YEAR FROM sale_date) AS year,
EXTRACT(MONTH FROM sale_date) AS month,
SUM(amount) AS total_sales
FROM sales
GROUP BY
EXTRACT(YEAR FROM sale_date),
EXTRACT(MONTH FROM sale_date)
ORDER BY total_sales DESC
LIMIT 1;
๐ก Explanation:
This query groups sales by year and month, calculates the total sales for each month, and returns the month with the highest sales.
Key parts:
โข EXTRACT YEAR FROM sale_date gets the year.
โข EXTRACT MONTH FROM sale_date gets the month.
โข SUM amount calculates total monthly sales.
โข ORDER BY total_sales DESC sorts from highest to lowest.
โข LIMIT 1 returns the top-performing month.
This question tests your understanding of:
Date Functions, Aggregate Functions SUM, GROUP BY, ORDER BY
๐ฏ Expected Output Example
Year: 2026, Month: 5, Total Sales: 245,000
๐ Alternative Handles Ties
SELECT
year,
month,
total_sales
FROM (
SELECT
EXTRACT(YEAR FROM sale_date) AS year,
EXTRACT(MONTH FROM sale_date) AS month,
SUM(amount) AS total_sales,
DENSE_RANK() OVER (
ORDER BY SUM(amount) DESC
) AS rnk
FROM sales
GROUP BY
EXTRACT(YEAR FROM sale_date),
EXTRACT(MONTH FROM sale_date)
) ranked
WHERE rnk = 1;
This version returns all months tied for the highest total sales.
๐ Date-based aggregation questions are among the most common in SQL interviews. Practice grouping data by Day, Week, Month, Quarter, Year. You'll encounter these patterns frequently in analytics and reporting roles.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the month with the highest total sales.
Assume the table structure: sales(sale_id, sale_date, amount)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
EXTRACT(YEAR FROM sale_date) AS year,
EXTRACT(MONTH FROM sale_date) AS month,
SUM(amount) AS total_sales
FROM sales
GROUP BY
EXTRACT(YEAR FROM sale_date),
EXTRACT(MONTH FROM sale_date)
ORDER BY total_sales DESC
LIMIT 1;
๐ก Explanation:
This query groups sales by year and month, calculates the total sales for each month, and returns the month with the highest sales.
Key parts:
โข EXTRACT YEAR FROM sale_date gets the year.
โข EXTRACT MONTH FROM sale_date gets the month.
โข SUM amount calculates total monthly sales.
โข ORDER BY total_sales DESC sorts from highest to lowest.
โข LIMIT 1 returns the top-performing month.
This question tests your understanding of:
Date Functions, Aggregate Functions SUM, GROUP BY, ORDER BY
๐ฏ Expected Output Example
Year: 2026, Month: 5, Total Sales: 245,000
๐ Alternative Handles Ties
SELECT
year,
month,
total_sales
FROM (
SELECT
EXTRACT(YEAR FROM sale_date) AS year,
EXTRACT(MONTH FROM sale_date) AS month,
SUM(amount) AS total_sales,
DENSE_RANK() OVER (
ORDER BY SUM(amount) DESC
) AS rnk
FROM sales
GROUP BY
EXTRACT(YEAR FROM sale_date),
EXTRACT(MONTH FROM sale_date)
) ranked
WHERE rnk = 1;
This version returns all months tied for the highest total sales.
๐ Date-based aggregation questions are among the most common in SQL interviews. Practice grouping data by Day, Week, Month, Quarter, Year. You'll encounter these patterns frequently in analytics and reporting roles.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค13
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โค2
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the customers who placed orders on three or more consecutive days.
Assume the table structure:
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
WITH consecutive_orders AS (
SELECT
customer_id,
order_date,
DATE_SUB(
order_date,
INTERVAL ROW_NUMBER() OVER (
PARTITION BY customer_id
ORDER BY order_date
) DAY
) AS grp
FROM (
SELECT DISTINCT
customer_id,
order_date
FROM orders
) t
)
SELECT
customer_id
FROM consecutive_orders
GROUP BY
customer_id,
grp
HAVING COUNT(*) >= 3;
๐ก Explanation:
This query identifies sequences of consecutive order dates for each customer.
โข ROW_NUMBER() assigns a sequence number to each order date per customer.
โข Subtracting the row number from the order date creates the same grp value for consecutive dates.
โข GROUP BY customer_id, grp groups each consecutive streak.
โข **HAVING COUNT(*) >= 3** returns customers with a streak of at least three consecutive days.
๐ฏ Expected Output Example
Customer ID
101
205
(Customer 101 ordered on June 1, 2, and 3. Customer 205 ordered on July 10, 11, and 12.)
๐ Tip for SQL Job Seekers:
The Gaps and Islands pattern is one of the most advanced and frequently discussed SQL interview topics. Master it for solving:
Consecutive login days, Consecutive purchases, Attendance streaks, Consecutive transactions, User activity analysis
Being comfortable with this pattern can set you apart in technical interviews.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the customers who placed orders on three or more consecutive days.
Assume the table structure:
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
WITH consecutive_orders AS (
SELECT
customer_id,
order_date,
DATE_SUB(
order_date,
INTERVAL ROW_NUMBER() OVER (
PARTITION BY customer_id
ORDER BY order_date
) DAY
) AS grp
FROM (
SELECT DISTINCT
customer_id,
order_date
FROM orders
) t
)
SELECT
customer_id
FROM consecutive_orders
GROUP BY
customer_id,
grp
HAVING COUNT(*) >= 3;
๐ก Explanation:
This query identifies sequences of consecutive order dates for each customer.
โข ROW_NUMBER() assigns a sequence number to each order date per customer.
โข Subtracting the row number from the order date creates the same grp value for consecutive dates.
โข GROUP BY customer_id, grp groups each consecutive streak.
โข **HAVING COUNT(*) >= 3** returns customers with a streak of at least three consecutive days.
๐ฏ Expected Output Example
Customer ID
101
205
(Customer 101 ordered on June 1, 2, and 3. Customer 205 ordered on July 10, 11, and 12.)
๐ Tip for SQL Job Seekers:
The Gaps and Islands pattern is one of the most advanced and frequently discussed SQL interview topics. Master it for solving:
Consecutive login days, Consecutive purchases, Attendance streaks, Consecutive transactions, User activity analysis
Being comfortable with this pattern can set you apart in technical interviews.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค13
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๐ Start learning today. Build confidence. Crack interviews smarter. Move closer to your dream job.
โค6
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the customers who placed orders on three or more consecutive days.
Assume the table structure:
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
WITH consecutive_orders AS (
SELECT
customer_id,
order_date,
DATE_SUB(
order_date,
INTERVAL ROW_NUMBER() OVER (
PARTITION BY customer_id
ORDER BY order_date
) DAY
) AS grp
FROM (
SELECT DISTINCT
customer_id,
order_date
FROM orders
) t
)
SELECT
customer_id
FROM consecutive_orders
GROUP BY
customer_id,
grp
HAVING COUNT(*) >= 3;
๐ก Explanation:
This query identifies sequences of consecutive order dates for each customer.
โข ROW_NUMBER() assigns a sequence number to each order date per customer.
โข Subtracting the row number from the order date creates the same grp value for consecutive dates.
โข GROUP BY customer_id, grp groups each consecutive streak.
โข **HAVING COUNT(*) >= 3** returns customers with a streak of at least three consecutive days.
This question tests your understanding of: Common Table Expressions (CTEs), Window Functions (ROW_NUMBER()), Gaps and Islands Problem, Date Arithmetic.
๐ฏ Expected Output Example
Customer ID
101
205
(Customer 101 ordered on June 1, 2, and 3. Customer 205 ordered on July 10, 11, and 12.)
๐ Tip for SQL Job Seekers:
The Gaps and Islands pattern is one of the most advanced and frequently discussed SQL interview topics.
Master it for solving:
โข Consecutive login days
โข Consecutive purchases
โข Attendance streaks
โข Consecutive transactions
โข User activity analysis
Being comfortable with this pattern can set you apart in technical interviews.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the customers who placed orders on three or more consecutive days.
Assume the table structure:
orders(order_id, customer_id, order_date)
๐ ๐ฒ: Challenge accepted! ๐ช
WITH consecutive_orders AS (
SELECT
customer_id,
order_date,
DATE_SUB(
order_date,
INTERVAL ROW_NUMBER() OVER (
PARTITION BY customer_id
ORDER BY order_date
) DAY
) AS grp
FROM (
SELECT DISTINCT
customer_id,
order_date
FROM orders
) t
)
SELECT
customer_id
FROM consecutive_orders
GROUP BY
customer_id,
grp
HAVING COUNT(*) >= 3;
๐ก Explanation:
This query identifies sequences of consecutive order dates for each customer.
โข ROW_NUMBER() assigns a sequence number to each order date per customer.
โข Subtracting the row number from the order date creates the same grp value for consecutive dates.
โข GROUP BY customer_id, grp groups each consecutive streak.
โข **HAVING COUNT(*) >= 3** returns customers with a streak of at least three consecutive days.
This question tests your understanding of: Common Table Expressions (CTEs), Window Functions (ROW_NUMBER()), Gaps and Islands Problem, Date Arithmetic.
๐ฏ Expected Output Example
Customer ID
101
205
(Customer 101 ordered on June 1, 2, and 3. Customer 205 ordered on July 10, 11, and 12.)
๐ Tip for SQL Job Seekers:
The Gaps and Islands pattern is one of the most advanced and frequently discussed SQL interview topics.
Master it for solving:
โข Consecutive login days
โข Consecutive purchases
โข Attendance streaks
โข Consecutive transactions
โข User activity analysis
Being comfortable with this pattern can set you apart in technical interviews.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค8
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You donโt need expensive courses to learn SQL, Excel, Python, Power BI, Tableau, and real-world analytics projects.
The Best YouTube channels for Data Analytics can help you build job-ready skills for internships, placements, and full-time analyst roles โ all for FREE.
๐ ๐๐ป๐ฟ๐ผ๐น๐น ๐๐ผ๐ฟ ๐๐ฅ๐๐๐:
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๐Start with one channel, stay consistent, build projects, and your Data Analytics career can genuinely take off.
You donโt need expensive courses to learn SQL, Excel, Python, Power BI, Tableau, and real-world analytics projects.
The Best YouTube channels for Data Analytics can help you build job-ready skills for internships, placements, and full-time analyst roles โ all for FREE.
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๐Start with one channel, stay consistent, build projects, and your Data Analytics career can genuinely take off.
โค4
๐๐ป๐๐ฒ๐ฟ๐๐ถ๐ฒ๐๐ฒ๐ฟ:
You have 2 minutes to solve this SQL query.
Find the product(s) that have never been ordered.
Tables:
products(product_id, product_name)
order_details(order_id, product_id, quantity)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
p.product_id,
p.product_name
FROM products p
LEFT JOIN order_details od
ON p.product_id = od.product_id
WHERE od.product_id IS NULL;
๐ก Explanation:
This query finds all products that do not have a matching record in the order_details table.
LEFT JOIN returns all products, regardless of whether they've been ordered. Products without matching orders will have NULL values for columns from order_details. WHERE od.product_id IS NULL filters only those products that have never been ordered.
This question tests your understanding of: LEFT JOIN, NULL handling, Finding unmatched records
๐ฏ Expected Output Example
Product ID Product Name
104 Wireless Mouse
118 USB Hub
125 Laptop Stand
๐ Alternative Using NOT EXISTS
SELECT
p.product_id,
p.product_name
FROM products p
WHERE NOT EXISTS (
SELECT 1
FROM order_details od
WHERE od.product_id = p.product_id
);
NOT EXISTS is often preferred because it handles NULL values correctly and can perform better than other approaches in many database systems.
๐ Tip for SQL Job Seekers:
Whenever you're asked to find records that don't exist in another table, consider these approaches:
LEFT JOIN ... IS NULL, NOT EXISTS โ (often the best choice), NOT IN (be cautious with NULL values)
Knowing the pros and cons of each approach is a common interview discussion point.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the product(s) that have never been ordered.
Tables:
products(product_id, product_name)
order_details(order_id, product_id, quantity)
๐ ๐ฒ: Challenge accepted! ๐ช
SELECT
p.product_id,
p.product_name
FROM products p
LEFT JOIN order_details od
ON p.product_id = od.product_id
WHERE od.product_id IS NULL;
๐ก Explanation:
This query finds all products that do not have a matching record in the order_details table.
LEFT JOIN returns all products, regardless of whether they've been ordered. Products without matching orders will have NULL values for columns from order_details. WHERE od.product_id IS NULL filters only those products that have never been ordered.
This question tests your understanding of: LEFT JOIN, NULL handling, Finding unmatched records
๐ฏ Expected Output Example
Product ID Product Name
104 Wireless Mouse
118 USB Hub
125 Laptop Stand
๐ Alternative Using NOT EXISTS
SELECT
p.product_id,
p.product_name
FROM products p
WHERE NOT EXISTS (
SELECT 1
FROM order_details od
WHERE od.product_id = p.product_id
);
NOT EXISTS is often preferred because it handles NULL values correctly and can perform better than other approaches in many database systems.
๐ Tip for SQL Job Seekers:
Whenever you're asked to find records that don't exist in another table, consider these approaches:
LEFT JOIN ... IS NULL, NOT EXISTS โ (often the best choice), NOT IN (be cautious with NULL values)
Knowing the pros and cons of each approach is a common interview discussion point.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค8
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Interviewer:
You have 2 minutes to solve this SQL query.
Find the employee or employees with the highest salary in the company without using MAX().
Me: Challenge accepted!
Explanation:
This query finds the highest-paid employee or employees without using the MAX() aggregate function.
โข DENSE_RANK() ranks salaries in descending order.
โข The highest salary receives a rank of 1.
โข The outer query filters only employees with salary_rank = 1.
โข If multiple employees share the highest salary, they are all returned.
This question tests your understanding of:
โข Window Functions using DENSE_RANK
โข Ranking Data
โข Handling Ties
โข Alternatives to Aggregate Functions
Expected Output Example
Employee: John, Salary: 120,000
Employee: Alice, Salary: 120,000
Both employees are returned because they share the highest salary.
Alternative Solution using NOT EXISTS
This solution works by returning employees for whom no other employee has a higher salary.
Tip for SQL Job Seekers:
Interviewers often ask you to solve problems without using aggregate functions like MAX() or MIN(). Learn multiple approaches using:
โข Window Functions
โข NOT EXISTS
โข Correlated Subqueries
โข Self Joins
Demonstrating alternative solutions shows strong SQL problem-solving skills.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
You have 2 minutes to solve this SQL query.
Find the employee or employees with the highest salary in the company without using MAX().
Me: Challenge accepted!
SELECT
employee_id,
employee_name,
salary
FROM (
SELECT
employee_id,
employee_name,
salary,
DENSE_RANK() OVER (ORDER BY salary DESC) AS salary_rank
FROM employees
) ranked
WHERE salary_rank = 1;
Explanation:
This query finds the highest-paid employee or employees without using the MAX() aggregate function.
โข DENSE_RANK() ranks salaries in descending order.
โข The highest salary receives a rank of 1.
โข The outer query filters only employees with salary_rank = 1.
โข If multiple employees share the highest salary, they are all returned.
This question tests your understanding of:
โข Window Functions using DENSE_RANK
โข Ranking Data
โข Handling Ties
โข Alternatives to Aggregate Functions
Expected Output Example
Employee: John, Salary: 120,000
Employee: Alice, Salary: 120,000
Both employees are returned because they share the highest salary.
Alternative Solution using NOT EXISTS
SELECT
employee_id,
employee_name,
salary
FROM employees e1
WHERE NOT EXISTS (
SELECT 1
FROM employees e2
WHERE e2.salary > e1.salary
);
This solution works by returning employees for whom no other employee has a higher salary.
Tip for SQL Job Seekers:
Interviewers often ask you to solve problems without using aggregate functions like MAX() or MIN(). Learn multiple approaches using:
โข Window Functions
โข NOT EXISTS
โข Correlated Subqueries
โข Self Joins
Demonstrating alternative solutions shows strong SQL problem-solving skills.
โค๏ธ React with โค๏ธ for more SQL interview challenges!
โค11
๐๐ฅ๐๐ ๐ฃ๐๐๐ต๐ผ๐ป ๐ฃ๐ฟ๐ผ๐ด๐ฟ๐ฎ๐บ๐บ๐ถ๐ป๐ด ๐๐ผ๐๐ฟ๐๐ฒ๐ | ๐ฐ ๐ ๐๐๐-๐ง๐ฎ๐ธ๐ฒ ๐๐ผ๐๐ฟ๐๐ฒ๐ ๐
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