How can i use a Count distinct values in SQL?

Question

How can I do in SQL a:

select count(distinct(field))
from table

and the final result don not count empty values?

example:

the final result should be 3 but it shows 4 (due to empty value).

Answer 1

Empty clearly does not mean NULL , because that is not counted. Let me assume it means an empty string, '' . If so:

select count(distinct nullif(field, ''))

Answer 2

@Gordon Linoff给出的答案就是解决方案！！