SQL中的（+）是什麼意思？

Question

這個SQL語句Where子句中的（+）是什麼意思？

SELECT p.FIRSTNAME, 
     p.LASTNAME, 
     p.LOGINNAME, 
     a.DESCRIPTION, 
     a.PERIPHERALNUMBER, 
     a.SUPERVISORAGENT, 
     t.ENTERPRISENAME, 
     t.DIALEDNUMBERID, 
     sp.FIRSTNAME AS SUPER_FIRSTNAME, 
     sp.LASTNAME AS SUPER_LASTNAME, 
     sp.LOGINNAME AS SUPER_LOGINNAME, 
     sa.PERIPHERALNUMBER AS SUPER_PERIPHERALNUMBER, 
     sa.SUPERVISORAGENT AS SUPER_SUPERVISORAGENT, 
     a.SKILLTARGETID, 
     a.PERSONID, 
     t.AGENTTEAMID, 
     sa.SKILLTARGETID AS SUPER_SKILLTARGETID, 
     sa.PERSONID AS SUPER_PERSONID 
FROM C2O.AGENT a, 
     C2O.PERSON p, 
     C2O.AGENT_TEAM_MEMBER tm, 
     C2O.AGENT_TEAM t, 
     C2O.AGENT sa, 
     C2O.PERSON sp 
WHERE a.PERSONID = p.PERSONID 
AND  a.SKILLTARGETID = tm.SKILLTARGETID(+) 
AND  tm.AGENTTEAMID = t.AGENTTEAMID(+) 
AND  t.PRISUPERVISORSKILLTARGETID = sa.SKILLTARGETID(+) 
AND  sa.PERSONID = sp.PERSONID(+) 
AND  a.DELETED = 'N' 
AND  p.LOGINENABLED = 'Y' 
AND  SUBSTR(a.PERIPHERALNUMBER,2,3) = 580; 

Answer 1

在Oracle SQL中，這是已棄用的outer join operator。

Answer 2

在舊的Oracle版本中，這意味着一個OUTER JOIN。

Answer 3

它是一個外部聯接運算符在SQL Server這將是*=和=*

Answer 4

在Oracle中，（+）指定該聯接是外連接（而不是內部聯接，因爲這隱含連接語法通常暗示）。

使它成爲外部聯接意味着即使該特定項爲空，該行也應該包含在結果中。