Substr on date oracle

Question

oracleに日付書式の列にsubstringを使用することは許されないと私は先生と議論しました。 substrは日付ではなく文字列で使用する必要があるためです。これについてあなたの意見は？クエリはこのだった

Lists those guest who were in one of our apartment at his/her birthday 

：

select * 
from ACCOMODATION.GUEST 
    JOIN ACCOMODATION.RESERVATION ON (USERNAME = GUEST_FK) 
where to_date(CONCAT(SUBSTR(ACCOMODATION.RESERVATION.ARRIVAL,0,2), substr(BDAY, 3, length(BDAY)))) 
     between ACCOMODATION.RESERVATION.ARRIVAL and ACCOMODATION.RESERVATION.LEAVE ; 

ACCOMODATION.RESERVATION.ARRIVAL、ACCOMODATION.RESERVATION.LEAVEとBDAYコメントのように日付

Answer 1

で、日付のTO_CHARを試し

TASTは、ということでした。すでにcharとして保存されている場合、あなたは大きな問題

select AG.*, AR.* 
from ACCOMODATION.GUEST AG 
INNER JOIN ACCOMODATION.RESERVATION AR 
    ON (USERNAME = GUEST_FK) 
where (to_char(AR.LEAVE, 'MMDD') > to_char(AR.ARRIVAL, 'MMDD') 
     and to_char(AG.BDAY, 'MMDD') 
      between to_char(AR.ARRIVAL, 'MMDD') 
        and to_char(AR.LEAVE, 'MMDD')) -- for those who did not stay over the new year 
or (to_char(AR.LEAVE, 'MMDD') < to_char(AR.ARRIVAL, 'MMDD') -- for those who stayed over new year 
    and (to_char(AG.BDAY, 'MMDD') >= to_char(AR.ARRIVAL, 'MMDD') 
     or to_char(AG.BDAY, 'MMDD') <= to_char(AR.LEAVE, 'MMDD')))