如何獲得當前員工狀態，辭職狀態，特殊期間新加入的狀態？

Question

我在這個表中有員工主表有empcode，empname，joindate，resigndate但沒有提及在master中輸入任何日期。 如何讓現有的員工，沒有員工的辭職，沒有員工在特定日期時間

爲前加入：

current employees -200 
resigned employees -25 
joined employees -10 
current status  -200+10=210-25=185 

這個每次我想以表格的形式

Answer 1

如果我們有一個日曆表或日期維度，查詢，查看...等，這變得更簡單。

/* example Calendar, just Months */ 
create table dbo.Calendar(
    MonthStart date primary key 
    , MonthEnd date 
); 

declare @FromDate date = '20000101'; 
declare @ThruDate date = '20301201'; 

with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n)) 
, d as (
    select DateValue=convert(date,dateadd(month 
     , row_number() over (order by (select 1)) -1, @fromdate)) 
    from   n as deka 
     cross join n as hecto 
     cross join n as kilo 
) 
insert into dbo.Calendar 
    select top (datediff(month, @FromDate, @ThruDate)+1) 
     MonthStart = dateadd(month, datediff(month, 0, DateValue), 0) 
    , MonthEnd  = dateadd(day,-1, dateadd(month, datediff(month, 0, DateValue)+1, 0)) 
    from d 
    order by DateValue; 

---

查詢使用common table expression然後sum(case when.. 1 else 0 end)

;with cte as (
select 
    c.MonthStart 
    , c.MonthEnd 
    , e.EmpCode 
    , e.JoinDate 
    , e.ResignDate 
from dbo.Calendar as c 
    inner join dbo.EmpMaster as e 
    on c.MonthEnd >= e.JoinDate 
    and c.MonthStart <= e.ResignDate 
) 
select 
    MonthStart 
    , MonthEnd 
    , CurrentEmployees = sum(
      case when JoinDate < MonthStart 
       then 1 else 0 end) 
    , Joined   = sum(
      case when JoinDate >= MonthStart and JoinDate <= MonthEnd 
       then 1 else 0 end) 
    , Resigned   = sum(
      case when ResignDate >= MonthStart and ResignDate <= MonthEnd 
       then 1 else 0 end) 
    , CurrentStatus = sum(
      case when ResignDate > MonthEnd 
       then 1 else 0 end) 
from cte 
group by 
    cte.MonthStart 
    , cte.MonthEnd 
order by cte.MonthStart; 

沒有CTE，以及使用count(case when ... then column else null end)代替：

select 
    MonthStart 
    , MonthEnd 
    , CurrentEmployees = count (
     case when JoinDate < MonthStart 
      then EmpCode else null end) 
    , Joined   = count (
     case when JoinDate >= MonthStart and JoinDate <= MonthEnd 
      then EmpCode else null end) 
    , Resigned   = count (
     case when ResignDate >= MonthStart and ResignDate <= MonthEnd 
      then EmpCode else null end) 
    , CurrentStatus = count (
     case when ResignDate > MonthEnd 
      then EmpCode else null end) 
from (
    select 
    c.MonthStart 
    , c.MonthEnd 
    , e.EmpCode 
    , e.JoinDate 
    , e.ResignDate 
from dbo.Calendar as c 
    inner join dbo.EmpMaster as e 
    on c.MonthEnd >= e.JoinDate 
    and c.MonthStart <= e.ResignDate 
    ) as cte 
group by cte.MonthStart, cte.MonthEnd 
order by cte.MonthStart 

每返回相同的結果：COUNT的`http://rextester.com/AEZTL76069

+------------+------------+------------------+--------+----------+---------------+ 
| MonthStart | MonthEnd | CurrentEmployees | Joined | Resigned | CurrentStatus | 
+------------+------------+------------------+--------+----------+---------------+ 
| 2010-01-01 | 2010-01-31 |    0 |  3 |  0 |    3 | 
| 2010-02-01 | 2010-02-28 |    3 |  1 |  0 |    4 | 
| 2010-03-01 | 2010-03-31 |    4 |  2 |  0 |    6 | 
| 2010-04-01 | 2010-04-30 |    6 |  1 |  0 |    7 | 
| 2010-05-01 | 2010-05-31 |    7 |  2 |  0 |    9 | 
| 2010-06-01 | 2010-06-30 |    9 |  1 |  0 |   10 | 
| 2010-07-01 | 2010-07-31 |    10 |  1 |  0 |   11 | 
| 2010-08-01 | 2010-08-31 |    11 |  2 |  0 |   13 | 
| 2010-09-01 | 2010-09-30 |    13 |  6 |  0 |   19 | 
| 2010-10-01 | 2010-10-31 |    19 |  2 |  0 |   21 | 
| 2010-11-01 | 2010-11-30 |    21 |  1 |  0 |   22 | 
| 2010-12-01 | 2010-12-31 |    22 |  0 |  0 |   22 | 
+------------+------------+------------------+--------+----------+---------------+