sql/presto：如何查找每天之前存在但不存在于当天的记录

【问题标题】：sql/presto: how to find records that exist before but not current day for each daysql/presto：如何查找每天之前存在但不存在于当天的记录
【发布时间】：2021-12-08 19:26:02
【问题描述】：

我有如下数据：

而想要的结果是查找对于每一天，在这一天之前消失的记录。期望的结果：

disappeared_item   day_of_interest
        b           2   (as of the second day, only b disappeared)
       b,c          3   (as of the fourth day, b and c disappeared)

我想找出每个项目的最大（天），但在如何获取每天累积的项目方面得到了堆栈

【问题讨论】：

标签： mysql sql data-manipulation presto

【解决方案1】：

WITH 
items AS ( SELECT DISTINCT item
           FROM test ),
days AS ( SELECT DISTINCT day
           FROM test )
SELECT GROUP_CONCAT(items.item) disappeared_item,
       days.day day_of_interest
FROM items
CROSS JOIN days
WHERE EXISTS ( SELECT NULL 
               FROM test
               WHERE test.item = items.item
                 AND test.day < days.day )
  AND NOT EXISTS ( SELECT NULL 
                   FROM test
                   WHERE test.item = items.item
                     AND test.day = days.day )
GROUP BY days.day;

https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=c35dbe8b9b0a0e00f69c542a70be4bfc

【讨论】：