Distinct customers per region in Tableau: the SQL equivalent, with a worked example

{ FIXED [Region] : COUNTD([Customer]) }

Region	Team	Customer	Revenue	Seats	Date
North	Cedar	Aster	120	4	2026-01-05
North	Cedar	Aster	80	2	2026-02-05
North	Cedar	Birch	300	6	2026-01-12
North	Pine	Clover	90	3	2026-02-14
South	Elm	Dahlia	200	5	2026-01-08
South	Elm	Dahlia	100	2	2026-02-08
South	Ash	Fern	75	3	2026-01-20
South	Ash	Fern	25	1	2026-02-20

SELECT "Region", COUNT(DISTINCT Customer) AS result FROM input  GROUP BY "Region" ORDER BY "Region"

Runs the example above.

SELECT "Region", COUNT(DISTINCT Customer) AS result FROM input  GROUP BY "Region" ORDER BY "Region"

Written for this dialect; not run here.

SELECT `Region`, COUNT(DISTINCT Customer) AS result FROM input  GROUP BY `Region` ORDER BY `Region`

Written for this dialect; not run here.

Region	result
North	3
South	2

Same rows from the calculation and from the SQL in DuckDB.

Where a naive translation goes wrong

COUNT(Customer) counts invoice rows and therefore duplicates repeat customers.

SELECT "Region", COUNT(Customer) AS result FROM input  GROUP BY "Region" ORDER BY "Region"

Region	result
North	4
South	4

SELECT "Region", COUNT(DISTINCT Customer) AS result FROM input  GROUP BY "Region" ORDER BY "Region"

Region	result
North	3
South	2

{ FIXED [Region] : COUNTD([Customer]) }