oracle insert时先判断数据是否存在

[Spancer]

插入数据语句如下：
insert into tableA
(id, i_id,some_id,selfcolumn)
select sd_cust_pk_seq.nextval,
tb.id,
tc.id,
mydata
from tableB tb
cross join tableC tc
where tb.column?= '..'
and tc.column?= '..'

如何在执行该语句时，判断数据（select sd_cust_pk_seq.nextval,
tb.id,
tc.id,
mydata
from tableB tb
cross join tableC tc
where tb.column?= '..'
and tc.column?= '..'）是否已经存在呢？

本人试过用：
insert into tableA
(id, i_id,some_id,selfcolumn)
select sd_cust_pk_seq.nextval,
tb.id,
tc.id,
mydata
from tableB tb
cross join tableC tc
where tb.column?= '..'
and tc.column?= '..'

and not exists

( select * from
tableA ta
join
tableB tb
on ( ta.id= tb.id)
cross join tableC tc
where tb.column?= '..'
and tc.column?= '..' )

感觉逻辑上不太对。。求助。

[crazylaa]

merge into 语句。

[majy]

如上，学习merge into语句的用法，这是个高效率的好东东

[gelyon]

merge into tableA
  (id, i_id,some_id,selfcolumn)
USING(select sd_cust_pk_seq.NEXTVAL id1,  
  tb.id id2,
  tc.id id3,
  mydata
  from tableB tb
 cross join tableC tc
 where tb.column?= '..'
  and tc.column?= '..' )   tableB
ON (tableA.id=tableB.id1 AND tableA.i_id=tableB.id2 AND tableA.some_id=tableB.id3)
WHEN NOT matched THEN 
INSERT VALUES(tableB.id1 ,tableB.id2,tableB.id3,tableB.mydata) ;

[Spancer]

嗯。merge into ,这个我知道。但是，好像merge into 好像比较新的语法，能不能考虑用left join 之类的呢？ 将tableB,tableC查询结果与tableA做left join?
insert into SD_CUST_&&NN._HOST.impl_lic_app_ftr
(ID, IMPL_ID, APP_FTR_ID, LIC_START_DATE, LIC_END_DATE, DATE_CREATED, CREATED_BY)
select SD_CUST_&&NN._HOST.sd_cust_pk_seq.nextval as v_id,
i_id,
af_id,
sysdate,
sysdate + 100000,
sysdate,
'Bug_10329_part2.sql' from
(select i.id as i_id, af.id af_id
from SD_CUST_&&NN._HOST.impl i
cross join SD_CUST_&&NN._HOST.app_ftr af
where i.code = 'SDMD'
and af.code = 'perm-app-config-write') tmp
left join SD_CUST_&&NN._HOST.impl_lic_app_ftr ilaf
on tmp.i_id = ilaf.impl_id
and
tmp.af_id = ilaf.app_ftr_id
and ilaf.impl_id is null;

[xman_78tom]

with t as (
select tb.bid, tc.cid, mydata
from tableB tb cross join tableC tc
where tb.column?= '..' and tc.column?= '..'
)
insert into tableA (id, i_id,some_id,selfcolumn)
select sd_cust_pk_seq.nextval, t.* from t
where not exist (select * from tableA 
 where t.bid=i_id and t.bid=some_id and t.mydata=selfcolumn);

[真的不知道取什么名]

--MERGE INTO 
MERGE INTO TABLEA a --要插入数据的表
using (select sd_cust_pk_seq.nextval seqid,  
       tb.id i_id,tc.id some_id,mydata selfcolumn
        from tableB tb
        cross join tableC tc
       where tb.column?= '..'
        and tc.column?= '..') t --要插入的表
on(t.seqid=a.id)--连接条件
insert
values (t.seqid, t.i_id,t.some_id,t.selfcolumn)