ZN in Tableau: the SQL equivalent, with a worked example

ZN([amount])

id	amount	units	score	other
1	-2.5	2	-0.8	3
2	0	0	0	4
3	1.5	3	0.25	2
4	4	4	0.5	8
5	9	5	0.8	11
6	16	6	1	14
7	null	7	null	9
8	4	8	-0.5	null

SELECT coalesce(amount,0) AS result FROM input ORDER BY id

Runs the example above.

SELECT coalesce(amount,0) AS result FROM input ORDER BY id

Written for this dialect; not run here.

SELECT coalesce(amount,0) AS result FROM input ORDER BY id

Written for this dialect; not run here.

id	amount	units	score	result
1	-2.5	2	-0.8	-2.5
2	0	0	0	0
3	1.5	3	0.25	1.5
4	4	4	0.5	4
5	9	5	0.8	9
6	16	6	1	16
7	null	7	null	0
8	4	8	-0.5	4

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

Where a naive translation goes wrong

Leaving the input unchanged preserves null rather than replacing it with zero.
Naive SQL
```
SELECT amount AS result FROM input ORDER BY id
```
id amount units score result
1 -2.5 2 -0.8 -2.5
2 0 0 0 0
3 1.5 3 0.25 1.5
4 4 4 0.5 4
5 9 5 0.8 9
6 16 6 1 16
7 null 7 null null
8 4 8 -0.5 4
Matches the calculation
```
SELECT coalesce(amount,0) AS result FROM input ORDER BY id
```
id amount units score result
1 -2.5 2 -0.8 -2.5
2 0 0 0 0
3 1.5 3 0.25 1.5
4 4 4 0.5 4
5 9 5 0.8 9
6 16 6 1 16
7 null 7 null 0
8 4 8 -0.5 4

ZN(number)