我试图更新表1，但没有设置表属性，因此出现了以下错误：“mismatched input”from'expecting set near'a'”

UPDATE a from table1 a ,(SELECT  
            DISTINCT SUBS SUB,
            Min(LINE) Over(PARTITION BY CONTRACT) LINE
        FROM 
            table1 K
        INNER JOIN 
        (
            SELECT
                CUSTOMER,
                FROM,
                TO,
                CONTRACT
            FROM
                Number_Change a
            JOIN 
                CONTRACTS b  ON a.CONTRACT=b.ID
        ) CH_SUB
        ON K.CUSTOMER = CH_SUB.CUSTOMER where (SUBO = Substr(FROM,4) OR SUBO = Substr(TO,4))
    )SRC 
     set  a.LINE = SRC.LINE,  TEC_UPDATE_DTTM = Current_Timestamp 
     WHERE SUBS = SUB;