Sandbox

SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (898, 899, 900, 974, 981, 975, 976)

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_categories	range	PRIMARY,p_category_id,idx_category_id	PRIMARY	3		7	Using index condition