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Curated ANSI SQL practice challenges across Window Functions, CTEs, complex Joins, and aggregations.

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#	TITLE & TOPIC TAGS	CATEGORY	DIFFICULTY
01	Select Product Name and Price from Inventory#SELECT#Projection	Basic Queries	Easy
02	Find Customer Orders Exceeding 500 Dollars#WHERE#Filtering	Filtering & Sorting	Easy
03	Find All Unique Customer Cities#DISTINCT#Deduplication	Filtering & Sorting	Easy
04	Sort Employees by Salary and Name#ORDER BY#Sorting	Filtering & Sorting	Easy
05	Find the Single Most Expensive Product#LIMIT#Top N	Filtering & Sorting	Easy
06	Find Employees with Salary Between 80,000 and 90,000#BETWEEN#Range Filter	Filtering & Sorting	Easy
07	Find Employees in HR, IT, or Engineering Departments#IN#Set Membership	Filtering & Sorting	Easy
08	Find Employees Whose Names Start with 'A'#LIKE#Wildcards	String Manipulation	Easy
09	Find Employees Without an Assigned Department#IS NULL#Null Handling	Data Quality	Easy
10	Count Total Number of Employees#COUNT#Aggregation	Aggregation & Grouping	Easy
11	Calculate Total Salary Payroll of All Employees#SUM#Aggregation	Aggregation & Grouping	Easy
12	Calculate Company-Wide Average Employee Salary#AVG#Mean Calculation	Aggregation & Grouping	Easy
13	Find Minimum and Maximum Employee Salaries#MIN#MAX	Aggregation & Grouping	Easy
14	Categorize Employees into Compensation Tiers#CASE#Salary Tier	Conditional Logic	Easy
15	Format Employee Name and Department into Single Label#CONCAT#Formatting	String Manipulation	Easy
16	Extract First Three Characters of Employee Name#SUBSTRING#Extraction	String Manipulation	Easy
17	Find Employees with Names Longer than Four Characters#LENGTH#Validation	String Manipulation	Easy
18	Format Employee Names to Uppercase and Departments to Lowercase#UPPER#LOWER	String Manipulation	Easy
19	Round Employee Salaries to One Decimal Place#ROUND#Precision	Numeric & Math	Easy
20	Select Order ID and Date Sorted by Order Date#STRFTIME#Date Formatting	Date & Time	Easy
21	Count Total Employees in Each Department#GROUP BY#Headcount	Aggregation & Grouping	Easy
22	Find Departments with More Than One Employee#HAVING#Threshold Filter	Aggregation & Grouping	Easy
23	Select Employee Names with Column Alias employee_name#AS#Aliasing	Basic Queries	Easy
24	Replace Missing Employee Departments with 'Unassigned'#COALESCE#Default Values	Data Quality	Easy
25	Retrieve Employee Names Along with Department Names#JOIN#Relational Mapping	Joins & Set Operations	Easy
26	Inner Join Employees and Departments to Report Salaries#INNER JOIN#Relational	Joins & Set Operations	Medium
27	Find Customers Who Have Never Placed an Order#LEFT JOIN#Anti-Join	Joins & Set Operations	Medium
28	List All Departments and Matching Employees Using Left Join#LEFT JOIN#Department Roster	Joins & Set Operations	Medium
29	Find Each Employee and Their Direct Manager Name#SELF JOIN#Manager Hierarchy	Joins & Set Operations	Medium
30	Generate Cartesian Cross Product of Employees and Departments#CROSS JOIN#Cartesian Product	Joins & Set Operations	Medium
31	Combine Distinct Names from Employees and Contractors#UNION#Set Union	Joins & Set Operations	Medium
32	Combine All Names from Employees and Contractors Including Duplicates#UNION ALL#Full Union	Joins & Set Operations	Medium
33	Find Employees Earning Higher Than Average Company Salary#Subquery#AVG Filter	Subqueries & CTEs	Medium
34	Find Customers with At Least One Order Using EXISTS#EXISTS#Semi-Join	Subqueries & CTEs	Medium
35	Find Customers with No Orders Using NOT EXISTS#NOT EXISTS#Anti-Join	Subqueries & CTEs	Medium
36	Find High Earners and Their Departments Using Common Table Expression#CTE#WITH Clause	Subqueries & CTEs	Medium
37	Assign Row Numbers to Employees by Salary within Department#ROW_NUMBER#Ordering	Window Functions	Medium
38	Rank Employees by Salary within Department Using RANK#RANK#Ties with Gaps	Window Functions	Medium
39	Rank Employees by Salary within Department Without Gaps Using DENSE_RANK#DENSE_RANK#Dense Ranking	Window Functions	Medium
40	Compare Employee Salary with Preceding Colleague Using LAG#LAG#Preceding Value	Window Functions	Medium
41	Compare Employee Salary with Subsequent Colleague Using LEAD#LEAD#Following Value	Window Functions	Medium
42	Calculate Running Total of Sales Ordered by Date#SUM OVER#Running Total	Window Functions	Medium
43	Find Top 2 Highest Paid Employees in Each Department#ROW_NUMBER#Top N	Window Functions	Medium
44	Find Duplicate User Emails in Accounts Table#HAVING#Duplicate Detection	Data Quality	Medium
45	Deduplicate User Records by Email and Name#DISTINCT#Deduplication	Data Quality	Medium
46	Calculate Total Spend per Customer from Orders#SUM#Customer LTV	Business Analytics	Medium
47	Aggregate Total Sales Revenue by Month#STRFTIME#Monthly Revenue	Time-Series & Analytics	Medium
48	Extract Category Attribute from JSON Logs#JSON#json_extract	String Manipulation	Medium
49	Pivot Department Sales by Year 2023 and 2024#Conditional SUM#Pivoting	Business Analytics	Medium
50	Reconcile Two Tables Using Full Outer Join#FULL OUTER JOIN#COALESCE	Joins & Set Operations	Medium
51	Find Highest-Paid Employee in Each Department#MAX#Department Top Earner	Subqueries & CTEs	Hard
52	Top 3 Highest-Paid Employees per Department#DENSE_RANK#Top 3 per Group	Window Functions	Hard
53	Identify Session Start Boundaries from Clickstream Events#LAG#Sessionization	Window Functions	Hard
54	Find Contiguous Active User Login Streaks#Gaps & Islands#Streak Detection	Gaps & Islands	Hard
55	Lookup Slowly Changing Company Dimension by Effective Date#SCD Type 2#Point-in-Time	Data Warehousing	Hard
56	Filter Incremental Records Past Watermark Timestamp#Watermark#Incremental Load	Data Engineering	Hard
57	Identify Employee Records Failing Quality Check Rules#Data Quality#Validation	Data Quality	Hard
58	Group User Signups into Monthly Acquisition Cohorts#Cohorts#STRFTIME	Time-Series & Analytics	Hard
59	Calculate Sales Performance Metrics by Geographic Region#KPIs#Aggregates	Business Analytics	Hard
60	Standardize and Clean Raw Staging User Records#TRIM#UPPER#Data Cleansing	Data Engineering	Hard
61	Second-Highest Salary in Each Department#DENSE_RANK#Runner-Up#Window Functions	Window Functions	Medium
62	Employees Earning Above Department Average#AVG#Subquery#Benchmark	Subqueries & Joins	Medium
63	Employees Out-Earning Their Direct Supervisors#SELF JOIN#Manager Hierarchy	Self Joins	Medium
64	Third-Highest Company Salary Without Paging#DENSE_RANK#DISTINCT#No Limit	Window Functions	Medium
65	Top 10 Percent Highest Earners per Department#CUME_DIST#Top Decile#Percentiles	Window Functions	Hard
66	Quartile Salary Distribution by Department#NTILE#Quartiles#Bucketing	Window Functions	Medium
67	Employee with Salary Closest to Department Average#AVG#ABS Difference#Window Functions	Window Functions	Hard
68	Employees Out-Earning at Least Three Department Peers#Correlated Subquery#COUNT#Filtering	Correlated Subqueries	Hard
69	Keep Most Recent Customer Record by Timestamp#ROW_NUMBER#Latest Timestamp#Deduplication	Deduplication	Medium
70	Identify Duplicate Customer Profiles on Composite Key#Composite Key#ROW_NUMBER#Deduplication	Deduplication	Medium
71	Audit Customer Email Changes Over Time#LAG#History Tracking#Audit Log	Window Functions	Medium
72	Extract Latest Customer Status from History#ROW_NUMBER#Status History#Latest State	Deduplication	Medium
73	Detect Account Reactivations from Closed to Active#State Transitions#Reactivation#HAVING	Window Functions	Hard
74	Find First and Most Recent Record per Customer#MIN_BY#MAX_BY#Lifecycle Snapshot	Aggregation & Grouping	Medium
75	Filter Duplicate Records Retaining Minimum ID#Self Join#Min ID Retention#Deduplication	Deduplication	Medium
76	Detect Conflicting Status Changes on Same Date#GROUP BY#HAVING#Audit Log	Data Quality	Medium
77	Find Managers with More Than Five Direct Reports#GROUP BY#HAVING#Hierarchy	Aggregation & Joins	Medium
78	Detect Salary Ties Within the Same Department#EXISTS#Salary Ties#Subqueries	Correlated Subqueries	Medium
79	Customers Who Purchased Product A but Never Product B#NOT EXISTS#Market Basket#Set Difference	Set Operations & Joins	Medium
80	Customers Who Bought Every Product in a Category#Relational Division#HAVING#COUNT DISTINCT	Relational Division	Hard
81	Products Purchased by 80 Percent of Active Customers#CTE#Market Penetration#Ratio Analysis	Business Analytics	Hard
82	Identify Active Customers Ordering Every Month of the Year#DATE_TRUNC#12-Month Coverage#Customer Loyalty	Time-Series	Medium
83	High-Value Customers Spending Above Global Average#LTV#CTE#Above Average	Business Analytics	Medium
84	Departments with Average Salary Exceeding Company Average#HAVING#AVG#Benchmark	Aggregation & Subqueries	Medium
85	Find Users with 3 Consecutive Days Login Streak#Gaps & Islands#Login Streaks#Window Functions	Gaps & Islands	Hard
86	Longest Consecutive Daily Login Streak per User#Gaps & Islands#MAX Streak#Window Functions	Gaps & Islands	Hard
87	Customers with Consecutive 3-Month Purchasing Cadence#Gaps & Islands#Cadence#Month Math	Time-Series	Hard
88	Calculate Days Elapsed Between First and Second Purchase#Repeat Purchase#Date Difference#ROW_NUMBER	Time-Series	Medium
89	Calculate Month-over-Month (MoM) Revenue Growth Rate#LAG#MoM Growth#Percentage Change	Financial Analytics	Medium
90	Compute 7-Day Trailing Rolling Average Revenue#Rolling Average#RANGE BETWEEN#Window Functions	Time-Series	Hard
91	Calculate 30-Day Trailing Rolling Spend per Customer#Rolling Sum#RANGE BETWEEN#Customer Spend	Time-Series	Hard
92	Customers Making Repeat Purchase Within 30 Days#Repeat Conversion#Date Math#Window Functions	Time-Series	Medium
93	Identify Inactive Transaction Periods Exceeding 30 Days#LEAD#Dormancy Gaps#Customer Inactivity	Gaps & Islands	Medium
94	Detect Employees Absent for 3 or More Consecutive Days#Gaps & Islands#Attendance#Absence Tracking	Gaps & Islands	Hard
95	Continuous Periods of High-Volume Daily Sales Exceeding 100K#Gaps & Islands#Sales Waves#Revenue Spikes	Gaps & Islands	Hard
96	Customer Activity Span: First Date, Last Date, and Active Days#MIN/MAX#COUNT DISTINCT#Customer Lifecycle	Aggregation & Grouping	Easy
97	Top 3 Products by Revenue for Each Month#DENSE_RANK#Monthly Top Products#E-commerce	Business Analytics	Hard
98	Top 2 Customers by Revenue for Each Month#DENSE_RANK#Top Spenders#Monthly Customers	Business Analytics	Medium
99	Customers with Increasing Monthly Spending for 3 Consecutive Months#Gaps & Islands#Spending Growth#Monthly Trends	Time-Series	Hard
100	Identify Immediately Churned Customers from Last Month#NOT EXISTS#Churn Analysis#Cohort Inactivity	Customer Analytics	Medium
101	Identify Users with 7-Day Continuous Login Streak#Gaps & Islands#7-Day Streak#Window Functions	Gaps & Islands	Hard
102	Calculate Year-over-Year (YoY) Revenue Growth Rate#YoY Growth#EXTRACT#LAG	Financial Analytics	Medium
103	Identify Continuous Active Periods for Each User#Gaps & Islands#User Activity#Streak Detection	Gaps & Islands	Hard
104	Measure Customer Retention at Day-1, Day-7, and Day-30#Cohort Retention#CROSS JOIN#Retention Curves	Cohort Analytics	Hard
105	Calculate Monthly Customer Repeat Rate Percentage#Repeat Rate#LAG#Customer Retention	SaaS Metrics	Hard
106	Top 10 Customers Revenue Concentration Share#Revenue Share#Pareto Analysis#Window Functions	Executive Analytics	Medium

#01Easy

Basic Queries

Select Product Name and Price from Inventory

#SELECT#Projection

#02Easy

Filtering & Sorting

Find Customer Orders Exceeding 500 Dollars

#WHERE#Filtering

#03Easy

Filtering & Sorting

Find All Unique Customer Cities

#DISTINCT#Deduplication

#04Easy

Filtering & Sorting

Sort Employees by Salary and Name

#ORDER BY#Sorting

#05Easy

Filtering & Sorting

Find the Single Most Expensive Product

#LIMIT#Top N

#06Easy

Filtering & Sorting

Find Employees with Salary Between 80,000 and 90,000

#BETWEEN#Range Filter

#07Easy

Filtering & Sorting

Find Employees in HR, IT, or Engineering Departments

#IN#Set Membership

#08Easy

String Manipulation

Find Employees Whose Names Start with 'A'

#LIKE#Wildcards

#09Easy

Data Quality

Find Employees Without an Assigned Department

#IS NULL#Null Handling

#10Easy

Aggregation & Grouping

Count Total Number of Employees

#COUNT#Aggregation

#11Easy

Aggregation & Grouping

Calculate Total Salary Payroll of All Employees

#SUM#Aggregation

#12Easy

Aggregation & Grouping

Calculate Company-Wide Average Employee Salary

#AVG#Mean Calculation

#13Easy

Aggregation & Grouping

Find Minimum and Maximum Employee Salaries

#MIN#MAX

#14Easy

Conditional Logic

Categorize Employees into Compensation Tiers

#CASE#Salary Tier

#15Easy

String Manipulation

Format Employee Name and Department into Single Label

#CONCAT#Formatting

#16Easy

String Manipulation

Extract First Three Characters of Employee Name

#SUBSTRING#Extraction

#17Easy

String Manipulation

Find Employees with Names Longer than Four Characters

#LENGTH#Validation

#18Easy

String Manipulation

Format Employee Names to Uppercase and Departments to Lowercase

#UPPER#LOWER

#19Easy

Numeric & Math

Round Employee Salaries to One Decimal Place

#ROUND#Precision

#20Easy

Date & Time

Select Order ID and Date Sorted by Order Date

#STRFTIME#Date Formatting

#21Easy

Aggregation & Grouping

Count Total Employees in Each Department

#GROUP BY#Headcount

#22Easy

Aggregation & Grouping

Find Departments with More Than One Employee

#HAVING#Threshold Filter

#23Easy

Basic Queries

Select Employee Names with Column Alias employee_name

#AS#Aliasing

#24Easy

Data Quality

Replace Missing Employee Departments with 'Unassigned'

#COALESCE#Default Values

#25Easy

Joins & Set Operations

Retrieve Employee Names Along with Department Names

#JOIN#Relational Mapping

#26Medium

Joins & Set Operations

Inner Join Employees and Departments to Report Salaries

#INNER JOIN#Relational

#27Medium

Joins & Set Operations

Find Customers Who Have Never Placed an Order

#LEFT JOIN#Anti-Join

#28Medium

Joins & Set Operations

List All Departments and Matching Employees Using Left Join

#LEFT JOIN#Department Roster

#29Medium

Joins & Set Operations

Find Each Employee and Their Direct Manager Name

#SELF JOIN#Manager Hierarchy

#30Medium

Joins & Set Operations

Generate Cartesian Cross Product of Employees and Departments

#CROSS JOIN#Cartesian Product

#31Medium

Joins & Set Operations

Combine Distinct Names from Employees and Contractors

#UNION#Set Union

#32Medium

Joins & Set Operations

Combine All Names from Employees and Contractors Including Duplicates

#UNION ALL#Full Union

#33Medium

Subqueries & CTEs

Find Employees Earning Higher Than Average Company Salary

#Subquery#AVG Filter

#34Medium

Subqueries & CTEs

Find Customers with At Least One Order Using EXISTS

#EXISTS#Semi-Join

#35Medium

Subqueries & CTEs

Find Customers with No Orders Using NOT EXISTS

#NOT EXISTS#Anti-Join

#36Medium

Subqueries & CTEs

Find High Earners and Their Departments Using Common Table Expression

#CTE#WITH Clause

#37Medium

Window Functions

Assign Row Numbers to Employees by Salary within Department

#ROW_NUMBER#Ordering

#38Medium

Window Functions

Rank Employees by Salary within Department Using RANK

#RANK#Ties with Gaps

#39Medium

Window Functions

Rank Employees by Salary within Department Without Gaps Using DENSE_RANK

#DENSE_RANK#Dense Ranking

#40Medium

Window Functions

Compare Employee Salary with Preceding Colleague Using LAG

#LAG#Preceding Value

#41Medium

Window Functions

Compare Employee Salary with Subsequent Colleague Using LEAD

#LEAD#Following Value

#42Medium

Window Functions

Calculate Running Total of Sales Ordered by Date

#SUM OVER#Running Total

#43Medium

Window Functions

Find Top 2 Highest Paid Employees in Each Department

#ROW_NUMBER#Top N

#44Medium

Data Quality

Find Duplicate User Emails in Accounts Table

#HAVING#Duplicate Detection

#45Medium

Data Quality

Deduplicate User Records by Email and Name

#DISTINCT#Deduplication

#46Medium

Business Analytics

Calculate Total Spend per Customer from Orders

#SUM#Customer LTV

#47Medium

Time-Series & Analytics

Aggregate Total Sales Revenue by Month

#STRFTIME#Monthly Revenue

#48Medium

String Manipulation

Extract Category Attribute from JSON Logs

#JSON#json_extract

#49Medium

Business Analytics

Pivot Department Sales by Year 2023 and 2024

#Conditional SUM#Pivoting

#50Medium

Joins & Set Operations

Reconcile Two Tables Using Full Outer Join

#FULL OUTER JOIN#COALESCE

#51Hard

Subqueries & CTEs

Find Highest-Paid Employee in Each Department

#MAX#Department Top Earner

#52Hard

Window Functions

Top 3 Highest-Paid Employees per Department

#DENSE_RANK#Top 3 per Group

#53Hard

Window Functions

Identify Session Start Boundaries from Clickstream Events

#LAG#Sessionization

#54Hard

Gaps & Islands

Find Contiguous Active User Login Streaks

#Gaps & Islands#Streak Detection

#55Hard

Data Warehousing

Lookup Slowly Changing Company Dimension by Effective Date

#SCD Type 2#Point-in-Time

#56Hard

Data Engineering

Filter Incremental Records Past Watermark Timestamp

#Watermark#Incremental Load

#57Hard

Data Quality

Identify Employee Records Failing Quality Check Rules

#Data Quality#Validation

#58Hard

Time-Series & Analytics

Group User Signups into Monthly Acquisition Cohorts

#Cohorts#STRFTIME

#59Hard

Business Analytics

Calculate Sales Performance Metrics by Geographic Region

#KPIs#Aggregates

#60Hard

Data Engineering

Standardize and Clean Raw Staging User Records

#TRIM#UPPER#Data Cleansing

#61Medium

Window Functions

Second-Highest Salary in Each Department

#DENSE_RANK#Runner-Up#Window Functions

#62Medium

Subqueries & Joins

Employees Earning Above Department Average

#AVG#Subquery#Benchmark

#63Medium

Self Joins

Employees Out-Earning Their Direct Supervisors

#SELF JOIN#Manager Hierarchy

#64Medium

Window Functions

Third-Highest Company Salary Without Paging

#DENSE_RANK#DISTINCT#No Limit

#65Hard

Window Functions

Top 10 Percent Highest Earners per Department

#CUME_DIST#Top Decile#Percentiles

#66Medium

Window Functions

Quartile Salary Distribution by Department

#NTILE#Quartiles#Bucketing

#67Hard

Window Functions

Employee with Salary Closest to Department Average

#AVG#ABS Difference#Window Functions

#68Hard

Correlated Subqueries

Employees Out-Earning at Least Three Department Peers

#Correlated Subquery#COUNT#Filtering

#69Medium

Deduplication

Keep Most Recent Customer Record by Timestamp

#ROW_NUMBER#Latest Timestamp#Deduplication

#70Medium

Deduplication

Identify Duplicate Customer Profiles on Composite Key

#Composite Key#ROW_NUMBER#Deduplication

#71Medium

Window Functions

Audit Customer Email Changes Over Time

#LAG#History Tracking#Audit Log

#72Medium

Deduplication

Extract Latest Customer Status from History

#ROW_NUMBER#Status History#Latest State

#73Hard

Window Functions

Detect Account Reactivations from Closed to Active

#State Transitions#Reactivation#HAVING

#74Medium

Aggregation & Grouping

Find First and Most Recent Record per Customer

#MIN_BY#MAX_BY#Lifecycle Snapshot

#75Medium

Deduplication

Filter Duplicate Records Retaining Minimum ID

#Self Join#Min ID Retention#Deduplication

#76Medium

Data Quality

Detect Conflicting Status Changes on Same Date

#GROUP BY#HAVING#Audit Log

#77Medium

Aggregation & Joins

Find Managers with More Than Five Direct Reports

#GROUP BY#HAVING#Hierarchy

#78Medium

Correlated Subqueries

Detect Salary Ties Within the Same Department

#EXISTS#Salary Ties#Subqueries

#79Medium

Set Operations & Joins

Customers Who Purchased Product A but Never Product B

#NOT EXISTS#Market Basket#Set Difference

#80Hard

Relational Division

Customers Who Bought Every Product in a Category

#Relational Division#HAVING#COUNT DISTINCT

#81Hard

Business Analytics

Products Purchased by 80 Percent of Active Customers

#CTE#Market Penetration#Ratio Analysis

#82Medium

Time-Series

Identify Active Customers Ordering Every Month of the Year

#DATE_TRUNC#12-Month Coverage#Customer Loyalty

#83Medium

Business Analytics

High-Value Customers Spending Above Global Average

#LTV#CTE#Above Average

#84Medium

Aggregation & Subqueries

Departments with Average Salary Exceeding Company Average

#HAVING#AVG#Benchmark

#85Hard

Gaps & Islands

Find Users with 3 Consecutive Days Login Streak

#Gaps & Islands#Login Streaks#Window Functions

#86Hard

Gaps & Islands

Longest Consecutive Daily Login Streak per User

#Gaps & Islands#MAX Streak#Window Functions

#87Hard

Time-Series

Customers with Consecutive 3-Month Purchasing Cadence

#Gaps & Islands#Cadence#Month Math

#88Medium

Time-Series

Calculate Days Elapsed Between First and Second Purchase

#Repeat Purchase#Date Difference#ROW_NUMBER

#89Medium

Financial Analytics

Calculate Month-over-Month (MoM) Revenue Growth Rate

#LAG#MoM Growth#Percentage Change

#90Hard

Time-Series

Compute 7-Day Trailing Rolling Average Revenue

#Rolling Average#RANGE BETWEEN#Window Functions

#91Hard

Time-Series

Calculate 30-Day Trailing Rolling Spend per Customer

#Rolling Sum#RANGE BETWEEN#Customer Spend

#92Medium

Time-Series

Customers Making Repeat Purchase Within 30 Days

#Repeat Conversion#Date Math#Window Functions

#93Medium

Gaps & Islands

Identify Inactive Transaction Periods Exceeding 30 Days

#LEAD#Dormancy Gaps#Customer Inactivity

#94Hard

Gaps & Islands

Detect Employees Absent for 3 or More Consecutive Days

#Gaps & Islands#Attendance#Absence Tracking

#95Hard

Gaps & Islands

Continuous Periods of High-Volume Daily Sales Exceeding 100K

#Gaps & Islands#Sales Waves#Revenue Spikes

#96Easy

Aggregation & Grouping

Customer Activity Span: First Date, Last Date, and Active Days

#MIN/MAX#COUNT DISTINCT#Customer Lifecycle

#97Hard

Business Analytics

Top 3 Products by Revenue for Each Month

#DENSE_RANK#Monthly Top Products#E-commerce

#98Medium

Business Analytics

Top 2 Customers by Revenue for Each Month

#DENSE_RANK#Top Spenders#Monthly Customers

#99Hard

Time-Series

Customers with Increasing Monthly Spending for 3 Consecutive Months

#Gaps & Islands#Spending Growth#Monthly Trends

#100Medium

Customer Analytics

Identify Immediately Churned Customers from Last Month

#NOT EXISTS#Churn Analysis#Cohort Inactivity

#101Hard

Gaps & Islands

Identify Users with 7-Day Continuous Login Streak

#Gaps & Islands#7-Day Streak#Window Functions

#102Medium

Financial Analytics

Calculate Year-over-Year (YoY) Revenue Growth Rate

#YoY Growth#EXTRACT#LAG

#103Hard

Gaps & Islands

Identify Continuous Active Periods for Each User

#Gaps & Islands#User Activity#Streak Detection

#104Hard

Cohort Analytics

Measure Customer Retention at Day-1, Day-7, and Day-30

#Cohort Retention#CROSS JOIN#Retention Curves

#105Hard

SaaS Metrics

Calculate Monthly Customer Repeat Rate Percentage

#Repeat Rate#LAG#Customer Retention

#106Medium

Executive Analytics

Top 10 Customers Revenue Concentration Share

#Revenue Share#Pareto Analysis#Window Functions