ORACLE 左连接 left join

ORACLE 左连接：
1.使用（+）表示：
SELECT A.OID,
       A.VALUE,
       A.NE_TYPE_OID,
       NVL(B.STATUS, '1') STATUS,
       A.TYPE,
       A.STARTTIME START_TIME
  FROM ALARM_E A, ALARM_E_CLEAR_TIME B
 WHERE A.OID = B.ALARM_EVENT_OID(+);       

              

2.使用left join表示：
SELECT A.OID,
       A.VALUE,
       A.NE_TYPE_OID,
       NVL(B.STATUS, '1') STATUS,
       A.TYPE,
       A.START_TIME
  FROM (select OID,
               KPI_DEFINE_OID,
               ALARM_DEFINE_OID,
               ALARM_THRESHOLD_LINE_OID,
               THRESHOLD_VALUE,
               REPORT_TIME,
               SLICE_TYPE,
               VALUE,
               COLOR_LEVEL,
               COMP_TYPE,
               NE_OID,
               NE_TYPE_OID,
               TYPE,
               STARTTIME START_TIME
          from ALARM_E) A
  left join (select STATUS, ALARM_EVENT_OID, END_TIME
               from ALARM_E_CLEAR_TIME) B on A.OID = B.ALARM_EVENT_OID;

 

上面的两个左连接语句显示的结果是相同的，左连接，（+放在等号的右边）