more than one value was returned by subquery - forum topic by MMM

Here is the query code that causes an error "more than one value was returned by subquery'. What is the best way to re-write the query so it can run efficiently and also without this error message to capture the mismatch either emp_dt or eff dt.  Any suggestion. I do really appreciate your help
SELECT
D.MIN_DERV_EFF_BEG_DT,
D. EMP_DT,
D.APPL_EMP_NBR,
D.EMP_NBR,
D.APPL_HISTORY_NBR,
D.APPL_GRP_NBR,
D.CREAT_DT FROM
(SELECT
DISTINCT B.EMP_DT,
A.DERV_EFF_BEG_DT AS MIN_DERV_EFF_BEG_DT,
A.APPL_EMP_NBR,
A.EMP_NBR,
A.APPL_HISTORY_NBR,
A.APPL_GRP_NBR,
A.CREAT_DT
 FROM   EMP_MTL A, EMP_CURR_MTL B
 WHERE
 B.BIRTH_DT > ( SELECT MIN(C.DERV_EFF_BEG_DT)
                            FROM EMP_MTL C
                            WHERE C.EMP_PI_JOIN_KEY = B.EMP_PI_JOIN_KEY
                            AND C.DERV_EFF_END_DT > CURRENT_DATE - 1095
                            GROUP BY C.EMP_NBR)
AND A.EMP_PI_JOIN_KEY  = B.EMP_PI_JOIN_KEY
AND A.DERV_EFF_END_DT > CURRENT_DATE - 1095
) D
JOIN
(
SELECT MIN(E.DERV_EFF_BEG_DT) AS MIN_DERV_EFF_BEG_DT , E.EMP_NBR
FROM  EMP_MTL E
WHERE E.DERV_EFF_END_DT > CURRENT_DATE - 1095
GROUP BY E.EMP_NBR
) F
ON D.EMP_NBR = F.EMP_NBR
AND D.MIN_DERV_EFF_BEG_DT= F.MIN_DERV_EFF_BEG_DT
ORDER BY D.EMP_NBR
;