根據同一選擇查詢中的另一個值選擇合併值？

Question

對不起，措辭不當的問題，但我使用下面的查詢鞏固客戶記錄：

select 
customer_key 
,FIRST_VALUE(name   IGNORE NULLS) OVER(PARTITION BY customer_key ORDER BY last_updated_date desc ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS NAME 
,FIRST_VALUE(county  IGNORE NULLS) OVER(PARTITION BY customer_key ORDER BY last_updated_date desc ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS COUNTRY 
,FIRST_VALUE(country_code IGNORE NULLS) OVER(PARTITION BY customer_key ORDER BY last_updated_date desc ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS COUNTRY_CODE 
from   customers cust 

這將選擇最近使用的customer_key客戶記錄。但對於國家/地區，我需要國家/地區代碼與國家/地區處於同一行，並使用country字段作爲驅動程序，但country_code列是NOT NULL字段。

例如，該原始數據：

customer Country Country_Code Date 
Dave  NULL  0   30/08/2017 
David  UK  1   29/08/2017 

需要顯示爲：

customer Country Country_Code 
Dave  UK  1 
Dave  UK  1 

但使用select查詢我目前使用我得到這個：

customer Country Country_Code 
Dave  UK  0 
Dave  UK  0 

有什麼建議嗎？

Answer 1

以下查詢應該可以工作。

SELECT FIRST_VALUE(NAME IGNORE NULLS) OVER (
     PARTITION BY customer_key ORDER BY last_updated_date DESC ROWS BETWEEN UNBOUNDED PRECEDING 
       AND UNBOUNDED FOLLOWING 
     ) AS NAME 
    ,FIRST_VALUE(county IGNORE NULLS) OVER (
     PARTITION BY customer_key ORDER BY last_updated_date DESC ROWS BETWEEN UNBOUNDED PRECEDING 
       AND UNBOUNDED FOLLOWING 
     ) AS COUNTRY 
    ,FIRST_VALUE((
      CASE 
       WHEN county IS NULL 
        THEN NULL 
       ELSE country_code 
       END 
      ) IGNORE NULLS) OVER (
     PARTITION BY customer_key ORDER BY last_updated_date DESC ROWS BETWEEN UNBOUNDED PRECEDING 
       AND UNBOUNDED FOLLOWING 
     ) AS COUNTRY_CODE 
FROM customers cust;