查询不是日期格式的特定属性的最新日期

Question

我需要设置一个查询，允许我选择组中最近更新的记录。如果两条记录有最新更新，则应选择更新历史最长的一条。如果两者都为空，或者两者具有相同的历史长度，则不应选择两者。这些字段是 varchar2 格式。第一条记录和最后一条记录的最后两位数字对应于这些记录的年份。历史长度中的字母对应于获取的数据类型的代码。下面是一个示例表，具有预期的结果：

| group_id  |    id |   First Record  |  Last Record    |     History Length    |
---------------------------------------------------------------------------------
|   a       |    1  |  record98       |    record16     | SNDAWEDSPSEDSYSEAOE   |
|   a       |    2  |  record97       |    record14     | AVNDAWEDSPSEDSYS      |
|   b       |    3  |  record96       |    record15     | BVNDAWEDSPSEDSYSEAOE  |
|   b       |    4  |  record98       |    record16     | UNDAWEDSPSEDSYSEAOP   |
|   b       |    5  |  record95       |    record16     | UNDAWEDSPSEDSYSEAOPHYE|
|   c       |    6  |  record96       |    record12     | BVNDAWEDSPSEDSYSE     |
|   c       |    7  |  record10       |   record15      | HUSIKD                |
|   d       |    8  |    null         |      null       |            null       |
|   d       |    9  |    null         |      null       |            null       |
|   e       |   10  |  record11       |  record16       |    ASIKSO             |
|   e       |   11  |  record11       |  record16       |    SIXLLO             |
-------------------------------------------------------------------------------------------------------------------

输出

| group_id  |    id |   First Record  |  Last Record    |     History Length    |
---------------------------------------------------------------------------------
|   a       |    1  |  record98       |    record16     | SNDAWEDSPSEDSYSEAOE   |
|   b       |    5  |  record95       |    record16     | UNDAWEDSPSEDSYSEAOPHYE|
|   c       |    7  |  record10       |   record15      | HUSIKD                |

历史不如最新记录重要，所以如果太难实现，我只需要最新记录的那一行。谢谢。

Answer 1

如果以下查询满足您的要求，请告诉我。

SELECT group_id,ID,first_record,last_record,history_length
FROM (
      SELECT group_id,ID,first_record,last_record,history_length,diff,
             MAX(LENGTH(history_length)) OVER (PARTITION BY group_id) max_len,
             count(1) OVER (PARTITION BY group_id,LENGTH(history_length)) cnt
      FROM (
           SELECT  group_id,ID,first_record,last_record,history_length,
                   count(1) OVER (PARTITION BY group_id,LENGTH(history_length)) cnt,
                   MAX(to_date(to_number(substr(last_record, 7,2)),'RR')-to_date(to_number(substr(first_record, 7,2)),'RR'))   OVER (PARTITION BY group_id) diff
           FROM (
                 SELECT group_id,ID,first_record,last_record,history_length,
                        MAX(last_record) OVER (PARTITION BY group_id) max_last_record
                 FROM  t
                 WHERE nvl(first_record,last_record) IS NOT NULL
                 )
                 WHERE last_record=max_last_record
           )
           WHERE   (to_date(to_number(substr(last_record, 7,2)),'RR')-to_date(to_number(substr(first_record, 7,2)),'RR'))=diff
      )
WHERE cnt=1
AND   LENGTH(history_length)=max_len;

Answer 2

我个人觉得 hemalp108 的回答很难理解；我更喜欢分解每一步。

以下是我如何使用 CTE 进行此操作的，其中每个后续 CTE 都是具有描述性名称的下一步，即

• 添加最大上次记录
• 然后按 Max LastRecord 搜索
• 然后添加 HistoryTally
• 然后添加 Max HistoryTally
• 然后按 Max HistoryTally 搜索
• 然后添加 HistoryTally 频率
• 然后按 HistoryTally 频率搜索
• 然后返回结果

附： SQLFiddle 不工作，所以我不得不在本地 SQL Server 中这样做（没有本地 Oracle）并尝试将其翻译回来！

WITH YourTable AS 
( SELECT * 
    FROM ( VALUES ( 'a',1,'record98','record16','SNDAWEDSPSEDSYSEAOE' ),
                  ( 'a',2,'record97','record14','AVNDAWEDSPSEDSYS' ),
                  ( 'b',3,'record96','record15','BVNDAWEDSPSEDSYSEAOE' ),
                  ( 'b',4,'record98','record16','UNDAWEDSPSEDSYSEAOP' ),
                  ( 'b',5,'record95','record16','UNDAWEDSPSEDSYSEAOPHYE' ),
                  ( 'c',6,'record96','record12','BVNDAWEDSPSEDSYSE' ),
                  ( 'c',7,'record10','record15','HUSIKD' ),
                  ( 'd',8,null,null,null),
                  ( 'd',9,null,null,null),
                  ( 'e',10,'record11','record16','ASIKSO' ),
                  ( 'e',11,'record11','record16','SIXLLO' )
) AS T ( group_id, id, FirstRecord, LastRecord, HistoryLength ) ),

AddMaxLastRecord AS
( SELECT *, MAX( LastRecord ) OVER ( PARTITION BY group_id ) MaxLastRecord
     FROM YourTable ),

SearchByMaxLastRecord AS
( SELECT group_id, id, FirstRecord, LastRecord, HistoryLength
     FROM AddMaxLastRecord
   WHERE LastRecord = MaxLastRecord ),

AddHistoryTally AS
( SELECT *, LEN( HistoryLength ) AS HistoryTally
     FROM SearchByMaxLastRecord ),

AddMaxHistoryTally AS
( SELECT *, MAX( HistoryTally ) OVER ( PARTITION BY group_id ) MaxHistoryTally
    FROM AddHistoryTally ),

SearchByMaxHistoryTally AS
( SELECT  group_id, id, FirstRecord, LastRecord, HistoryLength, HistoryTally
    FROM AddMaxHistoryTally
   WHERE HistoryTally = MaxHistoryTally ),

AddHistoryTallyFrequency AS
( SELECT *, COUNT( HistoryTally ) OVER ( PARTITION BY group_id ) AS HistoryTallyFreq
    FROM SearchByMaxHistoryTally ),

SearchByHistoryTallyFrequency AS
( SELECT group_id, id, FirstRecord, LastRecord, HistoryLength
    FROM AddHistoryTallyFrequency
   WHERE HistoryTallyFreq = 1 )

SELECT * 
  FROM SearchByHistoryTallyFrequency;