mysql - Get field from first table by foreign key from second -

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two tables: categories, , many-to-many relations:

categories id | name 1    first 2    second 3    third  relations parent | child 1        2 1        3

how can result?:

first | second first | third

i can 

select c.name, r.child  categories c  left join relations r on c.id = r.parent

and result is

first | 2 first | 3

so, how can child name in table? 

select c1.name, c2.name relations r left join categories c1 on r.parent = c1.id left join categories c2 on r.child = c2.id c1.id = 1

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