Error in the result

Question

I am in this practice
https://www.sololearn.com/en/learn/courses/sql-intermediate/code-coach/5041696371?returnUrl=/en/learn/courses/sql-intermediate/lesson/5041541097?p=8

my query:
SELECT firstname, lastname, salary,
CASE
WHEN salary <= 1500 THEN (salary*0.1)
WHEN salary >= 1501 OR salary <= 2000 THEN (salary*0.2)
WHEN salary >= 2001 THEN (salary*0.30)
END AS tax
FROM employees
ORDER BY lastname

The result shows that there is an error in my output compared to the expected output. Why?

Your code’s output is:

firstname,lastname,salary,tax
Amy,Anderson,2300,460.0
Lisa,Anderson,1300,130.0
David,Gibson,1750,350.0
Seth,Gray,2000,400.0
Nelson,Gross,1900,380.0
Bob,Peterson,1400,140.0
John,Smith,1500,150.0

Expected output is:

firstname,lastname,salary,tax
Amy,Anderson,2300,690.0
Lisa,Anderson,1300,130.0
David,Gibson,1750,350.0
Seth,Gray,2000,400.0
Nelson,Gross,1900,380.0
Bob,Peterson,1400,140.0
John,Smith,1500,150.0

Even if I change the query to
WHEN salary >= 2001 THEN (salary*0.50)
My output result is the same as above.

Please advise

Answer 1

use AND not OR.
also the conditions could be simplifed...

SELECT firstname, lastname, salary,
CASE
WHEN salary<=1500 THEN salary * 0.1
WHEN salary>1500 AND salary<=2000 THEN salary * 0.2
WHEN salary>2000 THEN salary * 0.3
END as tax
FROM employees
ORDER BY lastname