创建包含 2 列的时间范围 date_time

Question

我面临的问题是如何从 Teradata ANSI 中重叠的多个时间段中找到不同的时间段 SQL。

例如，附表包含多个重叠的时间段，我如何在 Teradata 中将这些时间段组合成 3 个唯一的时间段 SQL???

我想我可以在 python 中使用循环函数来完成，但不确定如何在 SQL

中完成

ID	Start Date	End Date
001	2005-01-01	2006-01-01
001	2005-01-01	2007-01-01
001	2008-01-01	2008-06-01
001	2008-04-01	2008-12-01
001	2010-01-01	2010-05-01
001	2010-04-01	2010-12-01
001	2010-11-01	2012-01-01

我的预期结果是：

ID	start_Date	end_date
001	2005-01-01	2007-01-01
001	2008-01-01	2008-12-01
001	2010-01-01	2012-01-01

Answer 1

这是一个缺口和孤岛问题。试试这个：

with u as 
(select ID, start_date, end_date,
case 
when start_date <= lag(end_date) over(partition by ID order by start_date, end_date) then 0 
else 1 end as grp
from table_name),
v as
(select ID, start_date, end_date,
sum(grp) over(partition by ID order by start_date, end_date) as island
from u)
select ID, min(start_date) as start_Date, max(end_date) as end_date
from v
group by ID, island;

Fiddle

基本上，您可以通过比较当前行的 start_date 和前一行的 end_date（按 start_date、end_date 排序）来识别“岛屿”，如果它先于那么它就是同一个岛。然后你可以滚动 sum() 来获取岛屿编号。最后 select 来自每个岛的 min(start_date) 和 max(end_date) 以获得所需的输出。

Answer 2

我在 Dbeaver 中尝试了它，但功能稍有变化，这可能会起作用：

select ID,Start_Date,End_Date
from 
(
select t.*,
dense_rank () over(partition by extract (year from Start_Date) order BY End_Date desc) drnk
from testing_123 t
) temp
where temp.drnk = 1
ORDER BY Start_Date;

Answer 3

试试这个

WITH a as (
  SELECT
    ID,
    LEFT(Start_Date, 4) as Year,
    MIN(Start_Date) as New_Start_Date
  FROM
    TAB1
  GROUP BY
    ID,
    LEFT(Start_Date, 4)
), b as (
  SELECT 
    a.ID,
    Year,
    New_Start_Date,
    End_Date
  FROM
    a
  LEFT JOIN
    TAB1
   ON LEFT(a.New_Start_Date, 4) = LEFT(TAB1.Start_Date, 4)
)
select 
  ID,
  New_Start_Date as Start_Date,
  MAX(End_Date)
from 
  b
GROUP BY
  ID,
  New_Start_Date;

示例：https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=97f91b68c635aebfb752538cdd752ace

Answer 4

从 Oracle 12 开始，您可以使用 MATCH_RECOGNIZE 执行 row-by-row 比较：

SELECT *
FROM   table_name
MATCH_RECOGNIZE(
  PARTITION BY id
  ORDER BY start_date
  MEASURES
    FIRST(start_date) AS start_date,
    MAX(end_date) AS end_date
  ONE ROW PER MATCH
  PATTERN (overlapping_ranges* last_range)
  DEFINE overlapping_ranges AS NEXT(start_date) <= MAX(end_date)
)

其中，对于示例数据：

CREATE TABLE table_name (ID, Start_Date, End_Date) AS
SELECT '001', DATE '2005-01-01', DATE '2006-01-01' FROM DUAL UNION ALL
SELECT '001', DATE '2005-01-01', DATE '2007-01-01' FROM DUAL UNION ALL
SELECT '001', DATE '2008-01-01', DATE '2008-06-01' FROM DUAL UNION ALL
SELECT '001', DATE '2008-04-01', DATE '2008-12-01' FROM DUAL UNION ALL
SELECT '001', DATE '2010-01-01', DATE '2010-05-01' FROM DUAL UNION ALL
SELECT '001', DATE '2010-04-01', DATE '2010-12-01' FROM DUAL UNION ALL
SELECT '001', DATE '2010-11-01', DATE '2012-01-01' FROM DUAL;

输出：

ID START_DATE END_DATE

001 2005-01-01 00:00:00 2007-01-01 00:00:00

001 2008-01-01 00:00:00 2008-12-01 00:00:00

001 2010-01-01 00:00:00 2012-01-01 00:00:00

db<>fiddle here

更新：替代查询

SELECT id,
       start_date,
       end_date
FROM   (
  SELECT id,
         dt,
         SUM(cnt) OVER (PARTITION BY id ORDER BY dt) AS grp,
         cnt
  FROM   (
    SELECT ID,
           dt,
           SUM(type) OVER (PARTITION BY id ORDER BY dt, ROWNUM) * type AS cnt
    FROM   table_name
    UNPIVOT (dt FOR type IN (start_date AS 1, end_date AS -1))
  )
  WHERE  cnt IN (1,0)
)
PIVOT (MAX(dt) FOR cnt IN (1 AS start_date, 0 AS end_date))

或者，不使用 UNPIVOT、PIVOT 或 ROWNUM 并且在 Oracle 和 PostgreSQL 中都有效的等效项：

SELECT id,
       MAX(CASE cnt WHEN 1 THEN dt END) AS start_date,
       MAX(CASE cnt WHEN 0 THEN dt END) AS end_date
FROM   (
  SELECT id,
         dt,
         SUM(cnt) OVER (PARTITION BY id ORDER BY dt) AS grp,
         cnt
  FROM   (
    SELECT ID,
           dt,
           SUM(type) OVER (PARTITION BY id ORDER BY dt, rn) * type AS cnt
    FROM   (
      SELECT r.*,
             ROW_NUMBER() OVER (PARTITION BY id ORDER BY dt ASC, type DESC) AS rn
      FROM   (
        SELECT id, 1 AS type, start_date AS dt FROM table_name
        UNION ALL
        SELECT id, -1 AS type, end_date AS dt FROM table_name
      ) r
    ) p
  ) s
  WHERE  cnt IN (1,0)
) t
GROUP BY id, grp

更新 2：另一种选择

SELECT id,
       MIN(start_date) AS start_date,
       MAX(end_Date) AS end_date
FROM   (
  SELECT t.*,
         SUM(CASE WHEN start_date <= prev_max THEN 0 ELSE 1 END)
           OVER (PARTITION BY id ORDER BY start_date) AS grp
  FROM   (
    SELECT t.*,
           MAX(end_date) OVER (
             PARTITION BY id ORDER BY start_date
             ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING
           ) AS prev_max
    FROM   table_name t
  ) t
) t
GROUP BY id, grp

db<>fiddle Oracle PostgreSQL

创建包含 2 列的时间范围 date_time

create time range with 2 columns date_time

sql

date

teradata

gaps-and-islands

更新：替代查询

更新 2：另一种选择

ID	START_DATE	END_DATE
001	2005-01-01 00:00:00	2007-01-01 00:00:00
001	2008-01-01 00:00:00	2008-12-01 00:00:00
001	2010-01-01 00:00:00	2012-01-01 00:00:00