SELECT
    CH0021.SAIKEN_NO
    ,CH0021.PRC_GRP_CD
    ,CH0021.PCRS_CD
    ,CH0021.PRC_SVC_CD
    ,CH0021.PRC_KMK_CD
    ,TO_CHAR(CH0021.AMNT)
    ,CH0021.SAIKEN_FIX_YM
    ,CH0021.ADD_DTM
    ,CH0021.UPD_DTM
    ,CH0021.ADD_UNYO_YMD
    ,CH0021.ADD_TRN_ID
    ,CH0021.UPD_UNYO_YMD
    ,CH0021.UPD_TRN_ID
FROM 
    CH_T_SAIKEN_UCWK CH0021
WHERE
    CH0021.SAIKEN_FIX_YM = (
                               SELECT
                                   CH0501_SUB.SEIKY_YM
                               FROM
                                   (
                                       SELECT
                                            CH0501.SEIKY_YM
                                       FROM 
                                           CH_M_PRC_SCHDL_TEIGI CH0501
                                       WHERE
                                               CH0501.EVENT_CD = :EVENT_CD
                                           AND CH0501.EVENT_YMD >= :OPEDATE
                                           AND CH0501.MK_FLG = '0'
                                       ORDER BY CH0501.EVENT_YMD ASC
                                   ) CH0501_SUB
                               WHERE
                                   ROWNUM = 1
                           )