UNION vs UNION ALL

EasySQL · PostgreSQL

Problem

Explain the difference between UNION and UNION ALL.

Asked in the Conceptual questions stage. Using the provided orders table, demonstrate the distinction by combining cities from delivered and returned orders.

Output

One column named city.
Include cities found in either order status.
Return each city once, ordered alphabetically with NULL last.

Schema

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer identifier
city	VARCHAR(100)	Customer delivery city
order_status	VARCHAR(30)	Current order status

Tablesorders

CodePostgreSQL

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