sql语句中有表.字段(+) 其中(+)是什么意思?
如:
SELECT                                                                                     
    D.ENV_AREA_NM AS ENV_AREA_NM,                                 
FROM                                                                                                  
    EAT110T P,                                                            
    (SELECT * FROM EAT060T WHERE USE_YN = 'Y') M                      
WHERE                                                                                 
D.ENV_AREA || SUBSTRING(D.DISCH_ID,1,2) = P.AD_ID
AND P.MAN_NO = M.MAN_NO(+)  有知道的高手 告知一下