CREATE OR REPLACE FUNCTION HAKSA.SF_HR_GET_DRNAPBU_CHK(IN_YEAR IN VARCHAR2, IN_HAKGI IN VARCHAR2, IN_HAKBEON IN VARCHAR2, IN_GBCD IN VARCHAR2 )  

RETURN VARCHAR2 IS  
    V_NAPBU_GBCD VARCHAR2(100);
    V_NAPBU_YN     VARCHAR2(100);
    V_NAPBU_DEUNGROKGEUM_GYE NUMBER(10);
    V_DEUNGROKGEUM_NAPBU_DT      VARCHAR2(100);
    V_SUNGMIN VARCHAR2(100);  
BEGIN  
  
        SELECT
                          CASE WHEN ( NVL(A.CHAEKJEONG_DEUNGROKGEUM_GYE,'0') - NVL(A.GAMMYEON_GYE,'0') - NVL(A.NAPBU_DEUNGROKGEUM_GYE,'0') ) = '0' 
                                    THEN '등록' 
                                   WHEN NVL(A.CHAEKJEONG_DEUNGROKGEUM_GYE, '0') < ( NVL(A.GAMMYEON_GYE,'0') - NVL(A.NAPBU_DEUNGROKGEUM_GYE,'0')  - NVL(B.HWANBUL_GYE, '0') )
                                    THEN '환불' ELSE '미등록' END AS NAPBU_GBCD 
                        , CASE WHEN ( NVL(A.CHAEKJEONG_DEUNGROKGEUM_GYE,'0') - NVL(A.GAMMYEON_GYE,'0') - NVL(A.NAPBU_DEUNGROKGEUM_GYE,'0') ) = '0' 
                                    THEN 'Y' ELSE 'N' END AS NAPBU_YN
                        , A.NAPBU_DEUNGROKGEUM_GYE
                        , A.DEUNGROKGEUM_NAPBU_DT
                        
         INTO  V_NAPBU_GBCD
                 , V_NAPBU_YN
                 , V_NAPBU_DEUNGROKGEUM_GYE
                 , V_DEUNGROKGEUM_NAPBU_DT
                        
        FROM
        (
            SELECT
                               YEAR  
                             , HAKGI
                             , HAKBEON
                             , MAX(CHAEKJEONG_DEUNGROKGEUM_GYE) AS CHAEKJEONG_DEUNGROKGEUM_GYE
                             , MAX(GAMMYEON_GYE) AS GAMMYEON_GYE
                             , SUM(NAPBU_DEUNGROKGEUM_GYE) AS NAPBU_DEUNGROKGEUM_GYE
                             , MIN(DEUNGROKGEUM_NAPBU_DT) AS DEUNGROKGEUM_NAPBU_DT
                     FROM HR_NAPBU_MST_M 
                     WHERE YEAR = IN_YEAR
                     AND HAKGI = IN_HAKGI
                     AND HAKBEON = IN_HAKBEON             
                     GROUP BY YEAR, HAKGI, HAKBEON    
        ) A
        LEFT OUTER JOIN 
        (
        SELECT
                           YEAR AS YEAR
                         , HAKGI  AS HAKGI
                         , HAKBEON  AS HAKBEON
                         , SUM(HWANBUL_GYE) AS HWANBUL_GYE
                 FROM HR_HWANBUL_M  
               WHERE YEAR = IN_YEAR
                    AND HAKGI = IN_HAKGI
                    AND HAKBEON = IN_HAKBEON
               GROUP BY YEAR,HAKGI,HAKBEON     
        ) B
        ON A.HAKBEON = B.HAKBEON
      AND A.YEAR = B.YEAR
      AND A.HAKGI = B.HAKGI        
  ;  
  
         IF IN_GBCD = '1' THEN
        V_SUNGMIN := V_NAPBU_GBCD;
    ELSIF IN_GBCD = '2' THEN
        V_SUNGMIN := V_NAPBU_DEUNGROKGEUM_GYE;
    ELSIF IN_GBCD = '3' THEN
        V_SUNGMIN := V_NAPBU_YN;
    ELSIF IN_GBCD = '4' THEN
        V_SUNGMIN := V_DEUNGROKGEUM_NAPBU_DT;   
    END IF;  
    
    RETURN V_SUNGMIN;
END;
/

값 4개를 던져 1.2.3.4조건에 따라서 리턴하는 펑션입니다.

실질적으로 4400건의 데이터를 이 펑션을 써서 조회하면 14초나 걸려버리네요 . 혹시 쿼리가 잘못됐는지 개선방법이 좀  조언받고 싶습니다.