在表中查找最小和最大数据列

Question

我有一个表格，可以准确地指定每个员工在特定办公室的日期和时间。

EmployeeTable 看起来像这样：

id	EmployeeID	DateP	TimeP
1	11111	1397/01/02	01:30
2	11111	1398/05/09	05:30
3	11111	1398/06/07	05:10
4	22222	1398/08/09	06:12
5	22222	1399/02/01	07:15
6	11111	1399/07/02	08:51
7	11111	1399/08/06	12:20
8	33333	1399/09/04	20:01
9	33333	1399/12/08	22:05
10	33333	1400/01/01	23:11
11	33333	1400/02/05	14:10
12	22222	1400/04/05	16:25

我想准确地选择每个员工在办公室时的最小和最大日期和时间：

id	EmployeeID	MinDateP	TimeMinDateP	MaxDateP	TimeMaxDateP
1	11111	1397/01/02	01:30	1398/06/07	05:10
2	22222	1398/08/09	06:12	1399/02/01	07:15
3	11111	1399/07/02	08:51	1399/08/06	12:20
4	33333	1399/09/04	20:01	1400/02/05	14:10
5	22222	1400/04/05	16:25	1400/04/05	16:25

我的SQL代码是：

with tab1 as 
(
    select * 
    from EmployeeTable
), tab2 as 
(
    select 
        t1.*,
        case when lag(t1.EmployeeID) over(order by t1.id) is null then 1
            when lag(t1.EmployeeID) over(order by t1.id) = t1.EmployeeID then 0
            else 1
       end lg
  from tab1 t1
)
, tab3 as (
select t1.*,
       sum(t1.lg) over(order by t1.id) grp
  from tab2 t1
)
select t1.EmployeeID,
       min(t1.DateP) as min,
       TimeP,
       max(t1.DateP)as max,
       TimeP
  from tab3 t1
 group by t1.EmployeeID, t1.grp

但上面的代码有错误。 每个人都可以帮助我吗？

Answer 1

这是一个空白和孤岛问题。解决此问题的一种方法是使用行数差异法：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (ORDER BY DateP, TimeP) rn1,
              ROW_NUMBER() OVER (PARTITION BY EmployeeID ORDER BY DateP, TimeP) rn2
    FROM EmployeeTable
),
cte2 AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY EmployeeID, rn1 - rn2
                                 ORDER BY DateP, TimeP) rn_first,
              ROW_NUMBER() OVER (PARTITION BY EmployeeID, rn1 - rn2
                                 ORDER BY DateP DESC, TimeP DESC) rn_last
    FROM cte
)

SELECT
    EmployeeID,
    MAX(CASE WHEN rn_first = 1 THEN DateP END) AS MinDateP,
    MAX(CASE WHEN rn_first = 1 THEN TimeP END) AS TimeMinDateP,
    MAX(CASE WHEN rn_last = 1  THEN DateP END) AS MaxDateP,
    MAX(CASE WHEN rn_last = 1  THEN TimeP END ) AS TimeMaxDateP
FROM cte2
GROUP BY
    EmployeeID,
    rn1 - rn2
ORDER BY
    MIN(DateP),
    MIN(TimeP);

请注意，如果您使用单个日期时间列来表示日期和时间，则完全不需要第二个 CTE 中的逻辑。像现在这样分开日期和时间通常是没有好处的。