SELECT 
  cscart_product_feature_variant_descriptions.variant 
FROM 
  cscart_product_features_values 
  LEFT JOIN cscart_product_feature_variant_descriptions ON cscart_product_feature_variant_descriptions.variant_id = cscart_product_features_values.variant_id 
  AND cscart_product_feature_variant_descriptions.lang_code = 'pl' 
WHERE 
  cscart_product_features_values.feature_id = 0 
  AND cscart_product_features_values.product_id = 1438