Query to find districts with at least one value in assets table

Question

This is my SQL query:

select count(*) from district

but i want to select only all districts that have at least 1 value in table assets stored. (can be more than 1)

so

select all districts that have at least 1 entry in assets

table assets: id name district_id

table district id name

How can I do that?

Answer 1

select count(*)
from district
where exists (
    select 1
    from assets
    where district_id = district.id
)