MySql - how to combine where clauses for both tables for one to many join?

Question

I have 2 tables :

sellers
id|name

locations
id|seller_id|name

Now I want to get sellers and join locations and combine attributes from both tables in where clause.

Initial query is :

SELECT 
    sellers.id
FROM sellers
JOIN locations.seller_id = sellers.id

I must add one more part because I don't want duplicated data :

SELECT 
    sellers.id
FROM sellers
JOIN locations on locations.seller_id = sellers.id
WHERE (
    SELECT id from locations
    WHERE locations.seller_id = sellers.id
    LIMIT 1
)

Now I can do the following

SELECT 
    sellers.id
FROM sellers
JOIN locations on locations.seller_id = sellers.id
WHERE (
    SELECT id from locations
    WHERE locations.seller_id = sellers.id
    LIMIT 1
)
AND (
    sellers.name = 'test'
    OR
    locations.name = 'test'
)

• problem here is that MySql will join first location and if name of that location is not "test" and there is location with name "test" for that seller it would not be not in results.

Any ideas?

UPDATED :

example with data :

sellers
id|name
1|test
2|test2


locations
id|seller_id|name
1|1|test3
2|2|test4
3|2|test
4|2|test


result should be 
[1, 2] but with my query it is [1] 

Answer 1

If you make your SQL simpler, the answer becomes simpler.

SELECT DISTINCT
    sellers.*
FROM sellers
    INNER JOIN locations on locations.seller_id = sellers.id
WHERE
    sellers.name = 'test'
    OR
    locations.name = 'test'

Answer 2

You can use Group By with Having :

SELECT sellers.id, 
       sellers.name, 
       SUM(locations.name = 'test') AS has_test_location 
FROM sellers
    INNER JOIN locations on locations.seller_id = sellers.id
GROUP BY sellers.id, sellers.name 
HAVING sellers.name = 'test' OR 
       has_test_location