SELECT 
  lang.name, 
  IF(
    cscart_ult_language_values.value IS NULL, 
    lang.value, cscart_ult_language_values.value
  ) as value 
FROM 
  cscart_language_values lang 
  LEFT JOIN cscart_ult_language_values ON cscart_ult_language_values.name = lang.name 
  AND company_id = 1 
  AND cscart_ult_language_values.lang_code = lang.lang_code 
WHERE 
  lang.lang_code = 'ru' 
  AND lang.name IN (
    'cannot_buy', 'no_products_selected', 
    'error_no_items_selected', 'delete_confirmation', 
    'text_out_of_stock', 'items', 'text_required_group_product', 
    'save', 'close', 'notice', 'warning', 
    'error', 'empty', 'text_are_you_sure_to_proceed', 
    'text_invalid_url', 'error_validator_email', 
    'error_validator_phone', 'error_validator_phone_mask', 
    'error_validator_integer', 'error_validator_multiple', 
    'error_validator_password', 'error_validator_required', 
    'error_validator_zipcode', 'error_validator_message', 
    'text_page_loading', 'error_ajax', 
    'text_changes_not_saved', 'text_data_changed', 
    'placing_order', 'file_browser', 
    'browse', 'more', 'text_no_products_found', 
    'cookie_is_disabled', 'insert_image', 
    'image_url', 'loading', 'cannot_buy', 
    'no_products_selected', 'error_no_items_selected', 
    'delete_confirmation', 'text_out_of_stock', 
    'items', 'text_required_group_product', 
    'save', 'close', 'notice', 'warning', 
    'error', 'empty', 'text_are_you_sure_to_proceed', 
    'text_invalid_url', 'error_validator_email', 
    'error_validator_phone', 'error_validator_phone_mask', 
    'error_validator_integer', 'error_validator_multiple', 
    'error_validator_password', 'error_validator_required', 
    'error_validator_zipcode', 'error_validator_message', 
    'text_page_loading', 'error_ajax', 
    'text_changes_not_saved', 'text_data_changed', 
    'placing_order', 'file_browser', 
    'browse', 'more', 'text_no_products_found', 
    'cookie_is_disabled', 'insert_image', 
    'image_url', 'loading'
  )

Query time 0.00343

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "88.81"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_ult_language_values",
          "access_type": "system",
          "possible_keys": [
            "PRIMARY"
          ],
          "rows_examined_per_scan": 0,
          "rows_produced_per_join": 1,
          "filtered": "0.00",
          "const_row_not_found": true,
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.20",
            "prefix_cost": "0.00",
            "data_read_per_join": "408"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value",
            "company_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "lang",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "lang_code",
            "name"
          ],
          "key_length": "392",
          "rows_examined_per_scan": 37,
          "rows_produced_per_join": 37,
          "filtered": "100.00",
          "index_condition": "((`db_emaika1`.`lang`.`lang_code` = 'ru') and (`db_emaika1`.`lang`.`name` in ('cannot_buy','no_products_selected','error_no_items_selected','delete_confirmation','text_out_of_stock','items','text_required_group_product','save','close','notice','warning','error','empty','text_are_you_sure_to_proceed','text_invalid_url','error_validator_email','error_validator_phone','error_validator_phone_mask','error_validator_integer','error_validator_multiple','error_validator_password','error_validator_required','error_validator_zipcode','error_validator_message','text_page_loading','error_ajax','text_changes_not_saved','text_data_changed','placing_order','file_browser','browse','more','text_no_products_found','cookie_is_disabled','insert_image','image_url','loading','cannot_buy','no_products_selected','error_no_items_selected','delete_confirmation','text_out_of_stock','items','text_required_group_product','save','close','notice','warning','error','empty','text_are_you_sure_to_proceed','text_invalid_url','error_validator_email','error_validator_phone','error_validator_phone_mask','error_validator_integer','error_validator_multiple','error_validator_password','error_validator_required','error_validator_zipcode','error_validator_message','text_page_loading','error_ajax','text_changes_not_saved','text_data_changed','placing_order','file_browser','browse','more','text_no_products_found','cookie_is_disabled','insert_image','image_url','loading')))",
          "cost_info": {
            "read_cost": "81.41",
            "eval_cost": "7.40",
            "prefix_cost": "88.81",
            "data_read_per_join": "14K"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value"
          ]
        }
      }
    ]
  }
}