SQL Exchange Null具有其他行值

Question

我是SQL的新手，我正在为VISW_FEATURE_COUNTRY和JOIN_COUNTRY列中的零值问题提供解决方案。 我希望该单元格从最近的日期（同一天，前一天或之后的同一天）获取非零值，而不是零值。 我已经附加了当前的结果和预期的结果屏幕截图。

CREATE VOLATILE TABLE new_base_count AS
(SELECT COALESCE(visw.employeemail, vnotw.employeemail) AS visw_employeemail
,COALESCE(visw.completed_at, vnotw.completed_at) AS visw_completed_at
,CASE WHEN visw.feature_country IN ('UK', 'UK/IE', 'AU') THEN 'UK'
ELSE visw.feature_country END AS visw_feature_country
,CASE WHEN visw_feature_country IN ('UK', 'UK/IE', 'AU') THEN 'UK'
ELSE visw_feature_country END AS join_country
FROM new_visw visw

FULL OUTER JOIN new_vnotw vnotw
ON visw.employeemail = vnotw.employeemail AND
visw.completed_at = vnotw.completed_at 
AND visw.feature_country = vnotw.feature_country
FULL OUTER JOIN new_vwonly vwo
ON (visw.employeemail = vwo.employee_email OR vnotw.employeemail = vwo.employee_email)
AND (visw.completed_at = vwo.completed_at OR vnotw.completed_at = vwo.completed_at)
AND (visw.feature_country = vwo.feature_country OR vnotw.feature_country = vwo.feature_country)
GROUP BY 1,2,3,4) WITH DATA ON COMMIT PRESERVE ROWS;

当前结果：

当前

预期结果：

预期

Answer 1

尝试last_value：

last_value(CASE WHEN visw.feature_country IN ('UK', 'UK/IE', 'AU') 
                THEN 'UK'
                ELSE visw.feature_country
           END IGNORE NULLS
over (partition by visw_employeemail
      order by visw_completed_at) AS visw_feature_country

类似于join_country