ORA-01858：找到一個非數字字符，其中數字是預期的 - oracle 10g

Question

我的問題是：對於每個會議，如果會議在2012年7月1日之前舉行，則顯示會議標題和“第一學期”字樣，如果會議在2012年7月1日或之后舉行，則顯示“第二學期”字樣。 對於包含“第一學期”或“第二學期”字樣的專欄，請填寫標題術語。 與之關聯的表是

CONFID             TITLE                    LOCATION          SDATE
------        --------------------       -------------------- ---------
c00001    Hydroinformatics                  Singapore          15-JUN-12
c00002    Ecological_modeling                Berlin            15-JUL-12
c00003    Computational_M                    London            25-MAY-12
c00004    Ecoinformatics                     Boston            22-AUG-12
c00005    Uncertainty_analysis               Athens            10-OCT-12
c00006    Large_databases                    Toronto           13-APR-12
c00007    Systems_analysis                    Boston           23-MAR-12
c00008    Systems_integration                 Tokyo            24-FEB-12
c00009    Aquatic_biology                      Helsinki        12-MAY-12
c00010    Information_systems                   Paris          08-JAN-12
c00011    Simulation_modeling                   Rome           01-SEP-12
c00012    DSS                                  Melbourne       18-DEC-12

我寫的sql語句是：

select C.Title, 'First term' as "Term" 
from Conference_C C 
where C.ConfID in (select C.Sdate 
                   from Conference_C C 
                   where C.Sdate < '1-July-12') 
union 
select C.Title, 'Second term' as "Term" 
from Conference_C C 
where C.ConfID in (select C.Sdate 
                     from Conference_C C 
                     where C.Sdate >= '1-July-12');

我收到以下錯誤：

select C.Title, 'First term' as "Term" from Conference_C C where C.ConfID
                                                                 *
ERROR at line 1:
ORA-01858: a non-numeric character was found where a numeric was expected

請澄清我哪里出錯了，任何幫助將不勝感激。 謝謝

Answer 1

您正在將ConfID （數字）與從內部查詢返回的Sdate （日期）進行比較：

where C.ConfID in (select C.Sdate 
                   from Conference_C C 
                   where C.Sdate < '1-July-12') 

您只需要一個像這樣的簡單SQL：

select C.Title, 'First term' as "Term" 
from Conference_C C 
where C.Sdate < '1-July-12'
union
select C.Title, 'Second term' as "Term" 
from Conference_C C 
where C.Sdate >= '1-July-12'

還由於兩個部分union是互斥的，一個union all可以使用（其執行更好，因為它不必消除重復）