将具有动态日期的行转换为列

Posted 2023-03-24

【中文标题】将具有动态日期的行转换为列

【英文标题】：Transforming rows having dynamic dates into columns

【发布时间】：2015-12-20 15:24:11

【问题描述】：

需要转换这个：

DATE            VALUE
18-DEC-15   2877544
17-DEC-15   2974276
16-DEC-15   4862020

进入

18-DEC-15   17-DEC-15   16-DEC-15
2877544     2974276     4862020

日期每天都会更新，我只需要选择最近的 3 个日期并将它们转换为具有以下相应值的列。 我尝试使用 Pivots，但我能够动态创建列标题。

【参考方案1】：

试试这个

WITH pivot_data AS (
            select date, value from table)
    SELECT *
    FROM   pivot_data
    PIVOT (
              max(value)        --<-- pivot_clause
          FOR table --<-- pivot_for_clause


);

【参考方案2】：

SQL 查询具有明确定义的列名，因此对于可变列名，您需要动态 SQL。但是，你可以用固定的名字做你想做的事：

select max(case when seqnum = 1 then value end) as MostRecentDay,
       max(case when seqnum = 2 then value end) as SecondMostRecentDay,
       max(case when seqnum = 3 then value end) as ThirdMostRecentDay
from (select t.*, dense_rank() over (order by date desc) as seqnum
      from t
     ) t;

您甚至可以添加三列来指定日期值：

select max(case when seqnum = 1 then value end) as MostRecentDay,
       max(case when seqnum = 2 then value end) as SecondMostRecentDay,
       max(case when seqnum = 3 then value end) as ThirdMostRecentDay,
       max(case when seqnum = 1 then date end) as MostRecentDate,
       max(case when seqnum = 2 then date end) as SecondMostRecentDate,
       max(case when seqnum = 3 then date end) as ThirdMostRecentDate           
from (select t.*, dense_rank() over (order by date desc) as seqnum
      from t
     ) t;

【参考方案3】：

使用Conditional Aggregate 旋转数据

select MAX(case when "DATE" = '18-DEC-15' then VALUE END) as '18-DEC-15',
       MAX(case when "DATE" = '17-DEC-15' then VALUE END) as '17-DEC-15',
       MAX(case when "DATE" = '16-DEC-15' then VALUE END) as '16-DEC-15'
from yourtable

注意：由于日期未知，需要使用EXECUTE IMMEDIATE

【讨论】：

您能否详细说明如何在此处使用 EXECUTE IMMEDIATE 功能？同样在尝试上述查询时，我收到一条错误消息，提示“未在预期的位置找到 FROM 关键字”。