SQL pattern · P07 · 17 problems

Joins

Graded problems on joins, from easy to hard.

17 problems · about 3 h in all
Start with problem 01Orders with Customer Name · 4 min
Learn it first · P07The LEFT JOIN that quietly becomes an INNERA right-table filter in WHERE drops the unmatched rows you meant to keep.Read the lesson →

Easy

6 problems · about 38 min
01Orders with Customer Name4 min →02Add a Category to Every Order Line5 min →03Payments with Their Order Amount5 min →04Refunds Traced to the Customer6 min →05Order Statistics for Every Customer8 min →06Reconcile CRM Contacts with Billing Accounts10 min →

Medium

6 problems · about 1 h
07Total Paid Revenue per Country12 min →08Assign Each Paid Order to Its Pricing Tier8 min →09Paid-Order Summary for Every Customer10 min →10Revenue by Region When Store Records Change12 min →11Price Each Order Line at Its Historical Price15 min →12Each Employee with Their Manager's Name7 min →

Hard

5 problems · about 1 h 20 min
13Every Order with Recent Refund Information15 min →14Paid Order Revenue and Item Quantity per Customer15 min →15Item and Payment Totals for Every Paid Order15 min →16Unique Customer Pairs from the Same Country10 min →17Convert International Orders Using Historical Exchange Rates20 min →
Up next · P08

The JOIN that answers a yes/no question with duplicates

15 practice problems. An INNER JOIN multiplies rows when you only needed to know a match exists.

Practise P08Read P08