Sql 如何选择显示自特定谓词出现的最后一刻起天数的行？

我有一个包含如下数据的表：

KEYWORD, CONVERSIONS, CREATED_AT
'Travel agent', 0, '2015-04-01'
'Travel agent', 0, '2015-04-02'
'Travel agent', 0, '2015-04-03'
'Travel agent', 0, '2015-04-04'
'Travel agent', 0, '2015-04-05'
'Travel agent', 0, '2015-04-06'
'Travel agent', 0, '2015-04-07'
'Travel agent', 0, '2015-04-08'
'Travel agent', 0, '2015-04-09'
'Travel agency vizier', 0, '2015-04-01'
'Travel agency vizier', 0, '2015-04-02'
'Travel agency vizier', 0, '2015-04-03'
'Travel agency vizier', 0, '2015-04-04'
'Travel agency vizier', 0, '2015-04-05'
'Travel agency vizier', 0, '2015-04-06'
'Travel agency vizier', 0, '2015-04-07'
'Travel agency vizier', 0, '2015-04-08'
'Travel agency vizier', 1, '2015-04-09'
'Coral', 0, '2015-04-01'
'Coral', 0, '2015-04-02'
'Coral', 0, '2015-04-03'
'Coral', 0, '2015-04-04'
'Coral', 0, '2015-04-05'
'Coral', 0, '2015-04-06'
'Coral', 0, '2015-04-07'
'Coral', 0, '2015-04-08'
'Coral', 0, '2015-04-09'
'Coral travel', 0, '2015-04-01'
'Coral travel', 0, '2015-04-02'
'Coral travel', 0, '2015-04-03'
'Coral travel', 0, '2015-04-04'
'Coral travel', 0, '2015-04-05'
'Coral travel', 0, '2015-04-06'
'Coral travel', 0, '2015-04-07'
'Coral travel', 0, '2015-04-08'
'Coral travel', 0, '2015-04-09'
'Egypt last minute', 1, '2015-04-01'
'Egypt last minute', 1, '2015-04-02'
'Egypt last minute', 0, '2015-04-03'
'Egypt last minute', 0, '2015-04-04'
'Egypt last minute', 0, '2015-04-05'
'Egypt last minute', 0, '2015-04-06'
'Egypt last minute', 0, '2015-04-07'
'Egypt last minute', 0, '2015-04-08'
'Egypt last minute', 0, '2015-04-09'
'Egypt holidays', 0, '2015-04-01'
'Egypt holidays', 0, '2015-04-02'
'Egypt holidays', 0, '2015-04-03'
'Egypt holidays', 0, '2015-04-04'
'Egypt holidays', 0, '2015-04-05'
'Egypt holidays', 0, '2015-04-06'
'Egypt holidays', 0, '2015-04-07'
'Egypt holidays', 0, '2015-04-08'
'Egypt holidays', 0, '2015-04-09'
'Exim', 0, '2015-04-01'
'Exim', 0, '2015-04-02'
'Exim', 0, '2015-04-03'
'Exim', 0, '2015-04-04'
'Exim', 0, '2015-04-05'
'Exim', 0, '2015-04-06'
'Exim', 0, '2015-04-07'
'Exim', 0, '2015-04-08'
'Exim', 0, '2015-04-09'
'Greece last minute', 0, '2015-04-03'
'Greece last minute', 0, '2015-04-04'
'Greece last minute', 0, '2015-04-05'
'Greece last minute', 0, '2015-04-06'
'Greece last minute', 0, '2015-04-07'
'Greece last minute', 0, '2015-04-08'
'Greece last minute', 0, '2015-04-09'
'Greece holidays', 0, '2015-04-01'
'Greece holidays', 0, '2015-04-02'
'Greece holidays', 0, '2015-04-03'
'Greece holidays', 0, '2015-04-04'
'Greece holidays', 0, '2015-04-05'
'Greece holidays', 0, '2015-04-06'
'Greece holidays', 0, '2015-04-07'
'Greece holidays', 0, '2015-04-08'
'Greece holidays', 0, '2015-04-09'
'Last-minute', 0, '2015-04-01'
'Last-minute', 0, '2015-04-02'
'Last-minute', 0, '2015-04-03'
'Last-minute', 0, '2015-04-04'
'Last-minute', 0, '2015-04-05'
'Last-minute', 0, '2015-04-06'
'Last-minute', 0, '2015-04-07'
'Last-minute', 0, '2015-04-08'
'Last-minute', 0, '2015-04-09'
'Last Minute', 1, '2015-04-01'
'Last Minute', 1, '2015-04-02'
'Last Minute', 0, '2015-04-03'
'Last Minute', 0, '2015-04-04'
'Last Minute', 0, '2015-04-05'
'Last Minute', 0, '2015-04-06'
'Last Minute', 0, '2015-04-07'
'Last Minute', 0, '2015-04-08'
'Last Minute', 0, '2015-04-09'
'Last Minute Egypt', 0, '2015-04-01'
'Last Minute Egypt', 0, '2015-04-02'
'Last Minute Egypt', 0, '2015-04-03'
'Last Minute Egypt', 0, '2015-04-04'
'Last Minute Egypt', 0, '2015-04-05'
'Last Minute Egypt', 0, '2015-04-06'
'Last Minute Egypt', 0, '2015-04-07'
'Last Minute Egypt', 0, '2015-04-08'
'Last Minute Egypt', 0, '2015-04-09'
'Last minute holidays', 0, '2015-04-01'
'Last minute holidays', 0, '2015-04-02'
'Last minute holidays', 0, '2015-04-03'
'Last minute holidays', 0, '2015-04-04'
'Last minute holidays', 0, '2015-04-05'
'Last minute holidays', 0, '2015-04-06'
'Last minute holidays', 0, '2015-04-07'
'Last minute holidays', 0, '2015-04-08'
'Last minute holidays', 0, '2015-04-09'
'Offer holiday', 0, '2015-04-01'
'Offer holiday', 0, '2015-04-02'
'Offer holiday', 0, '2015-04-03'
'Offer holiday', 0, '2015-04-04'
'Offer holiday', 0, '2015-04-05'
'Offer holiday', 0, '2015-04-06'
'Offer holiday', 0, '2015-04-07'
'Offer holiday', 0, '2015-04-08'
'Offer holiday', 0, '2015-04-09'
'Sun & fun', 0, '2015-04-01'
'Sun & fun', 0, '2015-04-02'
'Sun & fun', 0, '2015-04-03'
'Sun & fun', 0, '2015-04-04'
'Sun & fun', 0, '2015-04-05'
'Sun & fun', 0, '2015-04-06'
'Sun & fun', 0, '2015-04-07'
'Sun & fun', 0, '2015-04-08'
'Sun & fun', 2, '2015-04-09'
'Sun and fun', 0, '2015-04-01'
'Sun and fun', 0, '2015-04-02'
'Sun and fun', 0, '2015-04-03'
'Sun and fun', 0, '2015-04-04'
'Sun and fun', 0, '2015-04-05'
'Sun and fun', 0, '2015-04-06'
'Sun and fun', 0, '2015-04-07'
'Sun and fun', 0, '2015-04-08'
'Sun and fun', 1, '2015-04-09'
'Lodge', 0, '2015-04-01'
'Lodge', 0, '2015-04-02'
'Lodge', 0, '2015-04-03'
'Lodge', 0, '2015-04-04'
'Lodge', 0, '2015-04-05'
'Lodge', 1, '2015-04-06'
'Lodge', 1, '2015-04-07'
'Lodge', 1, '2015-04-08'
'Lodge', 0, '2015-04-09'
'Holiday greece', 0, '2015-04-01'
'Holiday greece', 0, '2015-04-02'
'Holiday greece', 0, '2015-04-03'
'Holiday greece', 0, '2015-04-04'
'Holiday greece', 0, '2015-04-05'
'Holiday greece', 0, '2015-04-06'
'Holiday greece', 0, '2015-04-07'
'Holiday greece', 0, '2015-04-08'
'Holiday greece', 0, '2015-04-09'
'Holiday', 4, '2015-04-01'
'Holiday', 4, '2015-04-02'
'Holiday', 1, '2015-04-03'
'Holiday', 1, '2015-04-04'
'Holiday', 1, '2015-04-05'
'Holiday', 3, '2015-04-06'
'Holiday', 3, '2015-04-07'
'Holiday', 3, '2015-04-08'
'Holiday', 3, '2015-04-09'
'Wakacje.pl', 13, '2015-04-01'
'Wakacje.pl', 13, '2015-04-02'
'Wakacje.pl', 1, '2015-04-03'
'Wakacje.pl', 1, '2015-04-04'
'Wakacje.pl', 1, '2015-04-05'
'Wakacje.pl', 6, '2015-04-06'
'Wakacje.pl', 6, '2015-04-07'
'Wakacje.pl', 6, '2015-04-08'
'Wakacje.pl', 4, '2015-04-09'
'Holiday 2014', 0, '2015-04-01'
'Holiday 2014', 0, '2015-04-02'
'Holiday greece', 1, '2015-04-01'
'Holiday greece', 1, '2015-04-02'
'Holiday greece', 0, '2015-04-03'
'Holiday greece', 0, '2015-04-04'
'Holiday greece', 0, '2015-04-05'
'Holiday greece', 0, '2015-04-06'
'Holiday greece', 0, '2015-04-07'
'Holiday greece', 0, '2015-04-08'
'Holiday greece', 0, '2015-04-09'
'Last-minute holiday', 0, '2015-04-01'
'Last-minute holiday', 0, '2015-04-02'
'Last-minute holiday', 0, '2015-04-03'
'Last-minute holiday', 0, '2015-04-04'
'Last-minute holiday', 0, '2015-04-05'
'Last-minute holiday', 0, '2015-04-06'
'Last-minute holiday', 0, '2015-04-07'
'Last-minute holiday', 0, '2015-04-08'
'Last-minute holiday', 1, '2015-04-09'
'Holiday last minute', 0, '2015-04-01'
'Holiday last minute', 0, '2015-04-02'
'Holiday last minute', 0, '2015-04-03'
'Holiday last minute', 0, '2015-04-04'
'Holiday last minute', 0, '2015-04-05'
'Holiday last minute', 0, '2015-04-06'
'Holiday last minute', 0, '2015-04-07'
'Holiday last minute', 0, '2015-04-08'
'Holiday last minute', 0, '2015-04-09'
'Vacation en', 0, '2015-04-01'
'Vacation en', 0, '2015-04-02'
'Vacation en', 0, '2015-04-03'
'Vacation en', 0, '2015-04-04'
'Vacation en', 0, '2015-04-05'
'Vacation en', 0, '2015-04-06'
'Vacation en', 0, '2015-04-07'
'Vacation en', 0, '2015-04-08'
'Vacation en', 0, '2015-04-09'
'Holiday in Greece', 0, '2015-04-01'
'Holiday in Greece', 0, '2015-04-02'
'Holiday in Greece', 0, '2015-04-03'
'Holiday in Greece', 0, '2015-04-04'
'Holiday in Greece', 0, '2015-04-05'
'Holiday in Greece', 0, '2015-04-06'
'Holiday in Greece', 0, '2015-04-07'
'Holiday in Greece', 0, '2015-04-08'
'Holiday in Greece', 1, '2015-04-09'
'Holidays abroad', 0, '2015-04-01'
'Holidays abroad', 0, '2015-04-02'
'Holidays abroad', 0, '2015-04-03'
'Holidays abroad', 0, '2015-04-04'
'Holidays abroad', 0, '2015-04-05'
'Holidays abroad', 0, '2015-04-06'
'Holidays abroad', 0, '2015-04-07'
'Holidays abroad', 0, '2015-04-08'
'Holidays abroad', 0, '2015-04-09'
'Holiday', 0, '2015-04-01'
'Holiday', 0, '2015-04-02'
'Holiday', 1, '2015-04-03'
'Holiday', 1, '2015-04-04'
'Holiday', 1, '2015-04-05'
'Holiday', 0, '2015-04-06'
'Holiday', 0, '2015-04-07'
'Holiday', 0, '2015-04-08'
'Holiday', 0, '2015-04-09'
'Egypt holiday last minute', 0, '2015-04-01'
'Egypt holiday last minute', 0, '2015-04-02'
'Egypt holiday last minute', 0, '2015-04-03'
'Egypt holiday last minute', 0, '2015-04-04'
'Egypt holiday last minute', 0, '2015-04-05'
'Egypt holiday last minute', 0, '2015-04-06'
'Egypt holiday last minute', 0, '2015-04-07'
'Egypt holiday last minute', 0, '2015-04-08'
'Egypt holiday last minute', 0, '2015-04-09'
'Holiday greece', 0, '2015-04-01'
'Holiday greece', 0, '2015-04-02'
'Holiday greece', 0, '2015-04-03'
'Holiday greece', 0, '2015-04-04'
'Holiday greece', 0, '2015-04-05'
'Holiday greece', 0, '2015-04-06'
'Holiday greece', 0, '2015-04-07'
'Holiday greece', 0, '2015-04-08'
'Holiday greece', 0, '2015-04-09'
'Travel abroad', 0, '2015-04-01'
'Travel abroad', 0, '2015-04-02'
'Travel abroad', 0, '2015-04-03'
'Travel abroad', 0, '2015-04-04'
'Travel abroad', 0, '2015-04-05'
'Travel abroad', 1, '2015-04-06'
'Travel abroad', 1, '2015-04-07'
'Travel abroad', 1, '2015-04-08'
'Travel abroad', 0, '2015-04-09'
'Vizier holidays', 1, '2015-04-01'
'Vizier holidays', 1, '2015-04-02'
'Vizier holidays', 0, '2015-04-03'
'Vizier holidays', 0, '2015-04-04'
'Vizier holidays', 0, '2015-04-05'
'Vizier holidays', 0, '2015-04-06'
'Vizier holidays', 0, '2015-04-07'
'Vizier holidays', 0, '2015-04-08'
'Vizier holidays', 0, '2015-04-09'
'Www vacation en ', 0,' 2015-04-01 '
'Www vacation en ', 0,' 2015-04-02 '
'Www vacation en ', 0,' 2015-04-03 '
'Www vacation en ', 0,' 2015-04-04 '
'Www vacation en ', 0,' 2015-04-05 '
'Www vacation en ', 0,' 2015-04-06 '
'Www vacation en ', 0,' 2015-04-07 '
'Www vacation en ', 0,' 2015-04-08 '
'Www vacation en ', 1,' 2015-04-09 '
'Trips', 0, '2015-04-01'
'Trips', 0, '2015-04-02'
'Trips', 0, '2015-04-03'
'Trips', 0, '2015-04-04'
'Trips', 0, '2015-04-05'
'Trips', 0, '2015-04-06'
'Trips', 0, '2015-04-07'
'Trips', 0, '2015-04-08'
'Trips', 0, '2015-04-09'
'Tours', 0, '2015-04-01'
'Tours', 0, '2015-04-02'
'Tours', 0, '2015-04-03'
'Tours', 0, '2015-04-04'
'Tours', 0, '2015-04-05'
'Tours', 0, '2015-04-06'
'Tours', 0, '2015-04-07'
'Tours', 0, '2015-04-08'
'Tours', 0, '2015-04-09'
'Trips abroad', 0, '2015-04-01'
'Trips abroad', 0, '2015-04-02'
'Trips abroad', 0, '2015-04-03'
'Trips abroad', 0, '2015-04-04'
'Trips abroad', 0, '2015-04-05'
'Trips abroad', 0, '2015-04-06'
'Trips abroad', 0, '2015-04-07'
'Trips abroad', 0, '2015-04-08'
'Trips abroad', 0, '2015-04-09'

这是谷歌分析API报告的一部分。

关键字

列包含用于广告网站的关键字，

CONVERSIONS

列包含在

CREATED\u at

中指定的日期的转换次数

特定谓词是日期范围：

---

WHERE'2015-04-01'您用
postgresql-9.4
标记了您的问题，因此您可以使用筛选的聚合：

select keyword, 
       max(created_at) filter (WHERE conversions > 0 AND created_at between '2015-04-01' AND '2015-04-09') as last_conversion_date
from conversion
group by keyword;

select keyword, 
       current_date - last_conversion_date as days_since_conversion, 
       last_conversion_date
from (
  select keyword, 
         max(created_at) filter (WHERE conversions > 0 AND created_at between '2015-04-01' AND '2015-04-09') as last_conversion_date
  from conversion
  group by keyword
) t
order by keyword;

这将为给定时间范围内的每个关键字和在

日期创建的最新

返回一行，但仅当存在转换时（这是过滤掉的必要条件，例如，
'Travel agent'，0'，2015-04-09'

要计算从那时起的天数，只需从
当前\u日期
中减去最新日期即可。为了不重复该表达式，可以更轻松地将查询放入该表达式的派生表中：

select keyword, 
       max(created_at) filter (WHERE conversions > 0 AND created_at between '2015-04-01' AND '2015-04-09') as last_conversion_date
from conversion
group by keyword;

select keyword, 
       current_date - last_conversion_date as days_since_conversion, 
       last_conversion_date
from (
  select keyword, 
         max(created_at) filter (WHERE conversions > 0 AND created_at between '2015-04-01' AND '2015-04-09') as last_conversion_date
  from conversion
  group by keyword
) t
order by keyword;

date'2015-04-01'
是SQL标准编写日期文字的语法，我更喜欢它，而不是只使用字符串的隐式日期样式

SQLFiddle在此：

SQLFiddle在

表达式而不是

过滤器

表达式时使用

大小写，因为
过滤器
在早期的Postgres版本中不可用。
以下是我的方法（可能与数据库无关，但不要相信我的话）：

请注意，就性能而言，这可能不是最好的解决方案。