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SELECT 
  cscart_product_files.*, 
  cscart_product_file_descriptions.file_name, 
  cscart_product_file_descriptions.license, 
  cscart_product_file_descriptions.readme 
FROM 
  cscart_product_files 
  LEFT JOIN cscart_product_file_descriptions ON cscart_product_file_descriptions.file_id = cscart_product_files.file_id 
  AND cscart_product_file_descriptions.lang_code = 'en' 
WHERE 
  1 = 1 
  AND cscart_product_files.product_id = 68201 
  AND preview_path != '' 
  AND cscart_product_files.status = 'A' 
ORDER BY 
  cscart_product_files.position asc, 
  cscart_product_file_descriptions.file_name asc

Query time 0.00048

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_product_files	ref	product_id	product_id	3	const	2	Using where; Using temporary; Using filesort
1	SIMPLE	cscart_product_file_descriptions	eq_ref	PRIMARY	PRIMARY	9	toolboxdigitalshop_dev.cscart_product_files.file_id,const	1	Using where

Result

file_id	product_id	file_path	preview_path	file_size	preview_size	agreement	max_downloads	total_downloads	activation_type	position	status	folder_id	file_name	license	readme
130005	68201	TMP106_One_Foot_In_The_Rave_-_Take_You_Back__Tempo_Trax_.mp3	TMP106_One_Foot_In_The_Rave_-_Take_You_Back__Tempo_Trax__SAMPLE.mp3	20144691	1440540	N	5	0	P	1	A		TMP106_One_Foot_In_The_Rave_-_Take_You_Back__Tempo_Trax_.mp3