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Recap - Invoices

Part of the Beyond the Basics section of Coddy's SQL journey — lesson 11 of 27.

Challenge

Easy

Available tables and columns:
<strong>invoices</strong>: <strong>id</strong>, <strong>code</strong>, <strong>customer_email</strong>

Every code is in the format 'INV-<year>-<number>' (e.g. 'INV-2026-00042'). Return:

id
year: the four-digit year as a string, e.g. '2026'
customer_domain: the domain part of customer_email, in lower case

Order by id.

Try it yourself

SELECT id,
       -- year extracted from code
       -- customer_domain from email
FROM invoices
ORDER BY id

All lessons in Beyond the Basics

1Conditional Logic

CASE WHEN CASE in ORDER BY COALESCE for NULLs NULLIF and IIF Recap - Attendance

4Set Operations

UNION vs UNION ALL INTERSECT EXCEPT Recap - Membership

2String Functions

LENGTH, UPPER, LOWER SUBSTR INSTR REPLACE and TRIM Concatenating with ||Recap - Invoices

5Recursive CTEs

A Number Sequence Walking a Hierarchy Recap - Org Chart

3Conditional Aggregation

COUNT with CASE SUM with CASE Pivoting Rows to Columns Recap - Traffic Sources

6Analytics Recipes

Top-N per Group Percentage of Total Running Total Keeping One Row per Key Recap - Top Customers