상황을 이해한 게 아니라  결과에 맞춘 쿼리예요. 

case가 달라지면 오류가 생길 것 같으네요. 

참고요 

with tmp as

(select 1111 as eno, 'a1234' as dno, 'AA' as ano, '20080101' as sdt, '20080321' as edt union all

select 1111 as eno, 'b1234' as dno, 'BB' as ano, '20080322' as sdt, '20091231' as edt union all

select 1111 as eno, 'b1234' as dno, 'CC' as ano, '20100101' as sdt, '20100630' as edt union all

select 1111 as eno, 'a1234' as dno, 'AA' as ano, '20100701' as sdt, '99991231' as edt union all

select 2222 as eno, 'c1234' as dno, 'AA' as ano, '20091001' as sdt, '20101231' as edt union all

select 2222 as eno, 'c1234' as dno, 'BB' as ano, '20110101' as sdt, '99991231' as edt )

select

eno,

dno,

sdt,

edt

from (

select

a.eno,

a.dno,

a.sdt,

isnull(b.edt, a.edt) as edt,

isnull(lag(a.dno) over (order by a.eno, a.sdt), 'x' + a.dno ) as prev_dno

from tmp a

left outer join tmp b

on a.eno = b.eno

and a.dno = b.dno

and convert(varchar(8), case

when a.edt != '99991231' then dateadd(dd, 1, a.edt)

else '99991231' end,

112) = b.sdt

) x

where

dno != prev_dno

CREATE TABLE #TEMP
(
    사번 VARCHAR(4),
    부서코드 VARCHAR(5),
    발령코드 VARCHAR(2),
    시작일 VARCHAR(8),
    종료일 VARCHAR(8)
)

INSERT INTO #TEMP VALUES('1111','a1234', 'AA', '20080101', '20080321')
INSERT INTO #TEMP VALUES('1111','b1234', 'BB', '20080322', '20091231')
INSERT INTO #TEMP VALUES('1111','b1234', 'CC', '20100101', '20100630')
INSERT INTO #TEMP VALUES('1111','a1234', 'AA', '20100701', '99991231')
INSERT INTO #TEMP VALUES('2222','c1234', 'AA', '20091001', '20101231')
INSERT INTO #TEMP VALUES('2222','c1234', 'BB', '20110101', '99991231')

------------------------------------------------------------------------------------
 

CREATE TABLE #DATA
(
    사번 VARCHAR(4),
    부서코드 VARCHAR(5),
    시작일 VARCHAR(8),
    종료일 VARCHAR(8),
    CNT INT
)

INSERT INTO #DATA
SELECT 
    A.사번, A.부서코드, A.시작일, A.종료일, 
    (
        SELECT COUNT(*) AS CNNT FROM 
        (
            SELECT 사번 FROM #TEMP
            GROUP BY 사번, 부서코드
        ) D
        WHERE A.사번 = D.사번
        GROUP BY 사번
    ) AS CNT
FROM #TEMP A

CREATE TABLE #RESULT
(
    사번 VARCHAR(4),
    부서코드 VARCHAR(5),
    시작일 VARCHAR(8),
    종료일 VARCHAR(8)
)

INSERT INTO #RESULT
SELECT 사번, 부서코드, MIN(시작일), MIN(종료일) FROM #DATA
GROUP BY 사번, 부서코드

INSERT INTO #RESULT
SELECT TOP 1 사번, 부서코드, 시작일, 종료일 FROM #DATA
WHERE CNT > 1
ORDER BY 시작일 DESC

SELECT * FROM #RESULT
ORDER BY 사번