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Sort customers with missing regions last · SQL scenario · D8LooP

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Sort customers with missing regions last

A regional report lists customers by region. Customers with no region belong at the bottom of the list, not the top, and the order must be identical every time the report runs. Return all five customers in that order.

Result columns · in this order

`customer_id`	The customer.
`full_name`	Their name.
`region`	Their region, or 'unassigned'.

How to approach it

Sort on a flag you compute yourself rather than relying on how this engine happens to place NULLs.

Sample input

shop_customersOne row per customer. region is NULL when unassigned.

customer_id	full_name	region	signed_up_on
c1	Ada Okafor	North	2025-11-02
c2	Bo Lindqvist	null	2025-12-14
c3	Chen Wei	South	2026-01-03
c4	Dara O'Neill	North	2026-01-20
c5	Eve Marsh	null	2026-02-01

5 rows — all rows shown.

Expected output

The exact result your query should return for this input.

customer_id	full_name	region
c1	Ada Okafor	North
c4	Dara O'Neill	North
c3	Chen Wei	South
c2	Bo Lindqvist	unassigned
c5	Eve Marsh	unassigned

5 rows — all rows shown.

Constraints

1Assigned regions come first, alphabetically.
2Customers with no region come last, shown as unassigned.
3Two customers share the region North; their relative order must be stable, so break the tie on customer_id.
4Do not sort by the unassigned label itself — that only works by accident of the alphabet.

Worked example

ORDER BY region alone puts c2 and c5 first, because SQLite sorts NULLs before every value. Other engines disagree: PostgreSQL puts them last by default, and NULLS FIRST / NULLS LAST is not available everywhere. Sorting on CASE WHEN region IS NULL THEN 1 ELSE 0 END first makes the intent explicit and behaves the same on every engine.

What this tests

That NULL ordering is engine-defined rather than standard, and that a sort without a tie-break is not reproducible.

SQL

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