INNER JOIN
Intermediate
Employee Department Names
List each employee's full name alongside their department name. Use INNER JOIN. Return columns: first_name, last_name, department_name.
25 XPSolve challenge
Interactive SQL practice
SQL JOIN Exercises
Practice combining related tables with INNER JOIN and LEFT JOIN exercises. These 40 interactive challenges use real schemas and instant query validation.
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Employee Department NamesMore exercises on this topic40 SQL challenges
Open Practice ArenaLEFT JOIN
Intermediate
Customers Without Orders
Find all customers who have never placed an order. Return columns: id, name, email.
25 XPSolve challenge
INNER JOIN
Intermediate
Revenue Per Customer
Calculate total revenue (sum of total_amount) per customer, showing customer name and total revenue, sorted by revenue descending. Return columns: customer_name, total_revenue. Order results by: total_revenue DESC.
25 XPSolve challenge
INNER JOIN
Intermediate
Product Sales Summary
For each product, show the total quantity sold and total revenue from order_items. Include product name. Return columns: product_name, total_quantity, total_revenue. Order results by: total_revenue DESC.
25 XPSolve challenge
INNER JOIN
Intermediate
Department Payroll Summary
Show each department name, employee count, and total payroll. Return columns: department_name, employee_count, total_payroll. Order results by: d.id.
25 XPSolve challenge
LEFT JOIN
Intermediate
Department Employee Coverage
Show all departments and their employee count, including departments with no employees. Return columns: department_name, employee_count. Order results by: d.id.
25 XPSolve challenge
LEFT JOIN
Intermediate
Product Revenue Including Unsold
Show every product and its revenue, using zero when it has no sales. Return columns: product_name, revenue. Order results by: p.id.
25 XPSolve challenge
INNER JOIN
Intermediate
Employee and Manager Names
List each managed employee together with their manager's name. Return columns: employee, manager. Order results by: e.id.
25 XPSolve challenge
INNER JOIN
Intermediate
Largest 1 Orders
Return the 1 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
Largest 2 Orders
Return the 2 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 3 Orders
Return the 3 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 4 Orders
Return the 4 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 5 Orders
Return the 5 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 6 Orders
Return the 6 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 7 Orders
Return the 7 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Intermediate
PRO
Largest 8 Orders
Return the 8 orders with the highest totals, including customer names. Return columns: order_id, customer_name, total_amount. Order results by: o.total_amount DESC, o.id.
25 XPSolve challenge
INNER JOIN
Advanced
Order Items With Quantity At Least 1
List order items with quantity at least 1, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
Order Items With Quantity At Least 2
List order items with quantity at least 2, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 3
List order items with quantity at least 3, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 4
List order items with quantity at least 4, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 5
List order items with quantity at least 5, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 6
List order items with quantity at least 6, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 7
List order items with quantity at least 7, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Order Items With Quantity At Least 8
List order items with quantity at least 8, including the product name. Return columns: order_id, product_name, quantity, unit_price. Order results by: oi.quantity DESC, oi.id.
50 XPSolve challenge
LEFT JOIN
Advanced
Customer Orders After 2024-01-01
Count each customer's orders placed on or after 2024-01-01. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
Customer Orders After 2024-01-12
Count each customer's orders placed on or after 2024-01-12. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-01-20
Count each customer's orders placed on or after 2024-01-20. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-02-01
Count each customer's orders placed on or after 2024-02-01. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-02-15
Count each customer's orders placed on or after 2024-02-15. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-03-01
Count each customer's orders placed on or after 2024-03-01. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-03-08
Count each customer's orders placed on or after 2024-03-08. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
LEFT JOIN
Advanced
PRO
Customer Orders After 2024-03-12
Count each customer's orders placed on or after 2024-03-12. Return columns: customer_name, order_count. Order results by: order_count DESC, customer_name.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Marketplace Sellers Covering Every Required Category
For each marketplace, return active sellers that offer at least one active listing in every category required by that marketplace. Ignore marketplaces with no requirements. Return marketplace_id and seller_id ordered by both columns. Return columns: marketplace_id, seller_id.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Products Frequently Bought Together Without Double Counting
Find canonical product pairs appearing together in at least two distinct completed baskets. Repeated lines for a product in one basket count once. Return product_a, product_b and basket_count, ordered by basket_count descending then product IDs. Return columns: product_a, product_b, basket_count.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Overlapping Subscription Periods per Customer
Return every pair of subscriptions for the same customer whose inclusive active periods overlap. A NULL end_date means the subscription is still active. Return customer_id, subscription_a, subscription_b, overlap_start and overlap_end; use NULL overlap_end for an open-ended overlap. Return columns: customer_id, subscription_a, subscription_b, overlap_start, overlap_end.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Latest Valid Address at Order Time
For every order, select the customer's address version valid at ordered_at. Validity is inclusive at valid_from and exclusive at valid_to; NULL valid_to is open-ended. If versions share valid_from, choose the highest address_id. Return order_id, address_id and city. Return columns: order_id, address_id, city.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Support Ticket Ownership Chain
Show the complete escalation ownership for open tickets: assigned agent, that agent's team lead, and the lead's support director. Exclude tickets whose chain is incomplete. Return ticket_id, agent_name, lead_name and director_name. Return columns: ticket_id, agent_name, lead_name, director_name.
50 XPSolve challenge
INNER JOIN
Advanced
PRO
Customers Shared Across Sales Representatives
Find canonical pairs of active sales representatives who currently share at least two distinct customers. Duplicate assignment history must not inflate the count. Return rep_a, rep_b and shared_customers. Return columns: rep_a, rep_b, shared_customers.
50 XPSolve challenge
LEFT JOIN
Expert
PRO
Employee Manager Lookup
Use a self LEFT JOIN to list every employee with their direct manager's first name. Return columns: id, first_name, manager_name. Order results by: e.id.
100 XPSolve challenge
INNER JOIN
Expert
PRO
Unmatched Inventory Movements Reconciliation
Reconcile ledger and scanner inventory movements by reference_code and product_id. Return records missing from either side or having different quantities. Emulate a full outer join in SQLite. Return reference_code, product_id, ledger_qty, scanner_qty and issue. Return columns: reference_code, product_id, ledger_qty, scanner_qty, issue.
100 XPSolve challenge
Concept guide
How to practice SQL JOIN
SQL JOINs combine rows from related tables. INNER JOIN keeps matching rows, while LEFT JOIN preserves every row from the left table and fills missing matches with NULL.
What to master
- • Choose join keys that represent the relationship
- • Qualify shared column names with table aliases
- • Understand how one-to-many joins affect row counts
- • Handle unmatched rows and NULL values deliberately
A reliable problem-solving workflow
- 1Identify the tables and required output columns.
- 2Find the primary-key and foreign-key relationship.
- 3Choose INNER JOIN or LEFT JOIN based on whether unmatched rows must remain.
- 4Run the query and verify both values and row count.
What is the difference between INNER JOIN and LEFT JOIN?
INNER JOIN returns only matching rows. LEFT JOIN returns every row from the left table and matching rows from the right table, using NULL when no match exists.
Why does a SQL JOIN create duplicate rows?
A one-to-many or many-to-many relationship can produce multiple result rows for one source row. Check the join keys and the relationship cardinality.