MySQL full text search, why am I getting Incorrect arguments to MATCH

Question

SELECT 
* 
FROM 
company c
INNER JOIN 
city ci ON ci.city_id = c.city_id
INNER JOIN 
state s ON s.state_id = c.state_id
WHERE 
MATCH (
c.name, ci.name, c.zipcode, s.name
)
AGAINST (
'los angeles'
)

Answer 1

Are you 100% sure "c.name, ci.name, c.zipcode, s.name" all exist?

Answer 2

Maybe all columns in MATCH (...) must be from the same table, because they must be fulltext indexed (and MySQL cannot create one index for data in multiple tables).