Beberapa Penggunaan Fungsi Syntax - Oracle

SELECT THN, BLN_THN, KODE, COUNTER_MAX, COUNTER, PANJANG,
        CASE WHEN PANJANG=4 THEN TO_CHAR(COUNTER)
                WHEN PANJANG=3 THEN TO_CHAR(0||COUNTER)
                WHEN PANJANG=2 THEN TO_CHAR(0||0||COUNTER)
                WHEN PANJANG=1 THEN TO_CHAR(0||0||0||COUNTER)
        END AS KODE_NEW
FROM ( SELECT  TO_CHAR(TGL_SLS_AR,'YYYY') THN, TO_CHAR(TGL_SLS_AR,'MM/YYYY') BLN_THN,
        SUBSTR(CD_SLS_AR,1,8) KODE,
        MAX(SUBSTR(CD_SLS_AR,9,LENGTH(CD_SLS_AR)-0)) COUNTER_MAX,
        (TO_CHAR((MAX(SUBSTR(CD_SLS_AR,9,LENGTH(CD_SLS_AR)-0))) )+1) COUNTER,
        LENGTH(TO_CHAR((MAX(SUBSTR(CD_SLS_AR,9,LENGTH(CD_SLS_AR)-0))) )+1) PANJANG
        FROM SLS_AR
        GROUP BY TO_CHAR(TGL_SLS_AR,'YYYY'),TO_CHAR(TGL_SLS_AR,'MM/YYYY') ,SUBSTR(CD_SLS_AR,1,8)
        ORDER BY TO_CHAR(TGL_SLS_AR,'YYYY') ,TO_CHAR(TGL_SLS_AR,'MM/YYYY')
        )