oracle 避免重复插入数据

using keyword :merge INTO ----------------------- merge into t1 using (select 1 a,3 b from dual) t2 on (t1.a = t2.a) when matched then update set t1.b = t1.bt2.b when not matched then insert (t1.a,t1.b) values(t2.a,t2.b) ------------------

using  keyword :merge INTO

-----------------------

merge into t1 using (select 1 a,3 b from dual) t2
    on (t1.a = t2.a)
    when matched then update set t1.b = t1.b+t2.b
   when not matched then insert (t1.a,t1.b) values(t2.a,t2.b)

 

------------------------------------

 

 

merge INTO SCNMON_DSMT_LV t1 USING
(SELECT 10916000 node_id FROM dual
) t2 ON (t1.lv_node_id = t2.node_id)
WHEN NOT matched THEN
  INSERT
    (
      t1.lv_key,
      t1.lv_node_id
    )
    VALUES
    (
      SEQ_SCNMON_DSMT_LV.nextval,
      t2.node_id
    );