Aggregation on quantile column-NTILE

Question

I have a CTE with below structure type-

WITH CTE1 AS (
  SELECT 
    , 
    DATE, 
    ID, 
    NAME, 
    CATEGORY, 
    SUBCATEGORY, 
    CHANNEL_NAME, 
    price, 
    discount, 
    NTILE(4) OVER (
      PARTITION BY CHANNEL_NAME 
      ORDER BY 
        PRICE
    ) as PRICE_QUARTILE 
  from 
    table 1
)
SELECT 
  DATE, 
  ID, 
  NAME, 
  CATEGORY, 
  SUBCATEGORY, 
  'all', 
  AVG(price) OVER (
    PARTITION BY PRICE_QUARTILE 
    ORDER BY 
      PRICE ROWS UNBOUND PRECEDING
  ) AS PRICE, 
  AVG(DISCOUNT) OVER (
    PARTITION BY PRICE_QUARTILE 
    ORDER BY 
      DISCOUNT ROWS UNBOUND PRECEDING
  ) AS DISCOUNT 
FROM 
  CTE1 
GROUP BY 
  1, 
  2, 
  3, 
  4, 
  5, 
  6 
UNION ALL 
SELECT 
  * 
FROM 
  CTE1

This is giving me an error as union is used and there is 1 column missing in select statement. I am not getting how to get the 'PRICE_QUARTILE' column as an aggregation in below select statement. Basically I have written above query to aggregation of prices for channel as 'overall' also did union to get individual channel's values too. Need to this NTILE(4) function to put price bands on products as to which product belongs to which price.