MySQL:bruge værdi fra en anden tabel som kolonnealias?

Forsøgte du at pakke aliaser ind i backqoutes?

SELECT 
  data.segment1 AS `type.segment1`,
  data.segment2 AS `type.segment2`,
  data.segment3 AS `type.segment3`
FROM something_obscure AS data
JOIN obscure_type AS type
ON data.obscure_type_id = type.id