Sankalan Tech Insights

Nov 13, 20264 min read

SQL Challenge: Rank Employees by Salary Within Each Department Using ROW_NUMBER()

#101 SQL Challenge: Rank Employees by Salary Within Each Department Using ROW_NUMBER() Introduction Imagine you are working on an employee salary report. The HR team wants to know who earns the highes

SQL Challenge Build a Customer Report Using JOIN, GROUP BY and CASE WHEN in Oracle SQL
Nov 12, 20265 min read
SQL Challenge: Can You Group Customers by Income Using CASE WHEN?
Nov 11, 20262 min read
Extract an Email Domain Using INSTR() and SUBSTR() in Oracle SQL
Nov 10, 20263 min read
SQL Tutorial: Clean Messy Employee Names Using TRIM(), LOWER(), and INITCAP()
Nov 9, 20264 min read

Can You Find Employees Who Joined This Month Using SQL? (Oracle TRUNC & ADD_MONTHS)
Your HR manager asks you to find all employees who joined during the current month. You could filter for November 2026, but would you have to change the query when December starts? Can you make it d
Nov 8, 20262 min read
SQL Challenge: Why Is Your SQL Query Still Returning NULL?
Imagine your manager asks you to prepare a salary report. Some employees have a bonus, while others have no bonus recorded. Your manager wants to see 0 instead of NULL for missing bonuses. You write a
Nov 4, 20262 min read
SQL Challenge: How to Get Employee Names and Department Names Using JOIN
Imagine your manager asks you to prepare a report showing each employee's name along with their department name. You have two tables: "employees" – stores employee details. "departments" – stores dep
Nov 4, 20262 min read
SQL EXISTS vs JOIN: Find Customers Who Have Placed an Order
#88 SQL Challenge: Can You Find Customers Who Have Placed an Order? Imagine your manager asks you to find all customers who have placed at least one order. You have two tables. Some customers have pla
Oct 31, 20263 min read
SQL: WHERE, ORDER BY, and LIMIT — Why Your Query May Return the Wrong Employees
A SQL query can run successfully and still return the wrong result. Imagine your manager asks you to find the three highest-paid employees in the IT department. You write a query, execute it, and get
Oct 30, 20263 min read
SQL Filtering and Sorting: 5 Mistakes That Can Change Your Query Results
A SQL query can execute without errors and still produce an unexpected result. It might return the wrong employees, sort salaries incorrectly, or select the wrong three records. The problem often lies
Oct 29, 20263 min read

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Latest articles

SQL Challenge: Rank Employees by Salary Within Each Department Using ROW_NUMBER()

SQL Challenge Build a Customer Report Using JOIN, GROUP BY and CASE WHEN in Oracle SQL

SQL Challenge: Can You Group Customers by Income Using CASE WHEN?

Extract an Email Domain Using INSTR() and SUBSTR() in Oracle SQL

SQL Tutorial: Clean Messy Employee Names Using TRIM(), LOWER(), and INITCAP()

Can You Find Employees Who Joined This Month Using SQL? (Oracle TRUNC & ADD_MONTHS)

SQL Challenge: Why Is Your SQL Query Still Returning NULL?

SQL Challenge: How to Get Employee Names and Department Names Using JOIN

SQL EXISTS vs JOIN: Find Customers Who Have Placed an Order

SQL: WHERE, ORDER BY, and LIMIT — Why Your Query May Return the Wrong Employees

SQL Filtering and Sorting: 5 Mistakes That Can Change Your Query Results