mysql查询使用连接显示数据？

I have two tables I want to display datas which are not in table 2 but exist in table 1 and after listing the datas.I want to add those datas in table 2. which join shall i use?please help me with the code

You need no join at all. You want data from table1 where no entry exists in table2. So use the EXISTS clause.

select something 
from table1 
where not exists 
(
  select *
  from table2 
  where table2.somekey = table1.somekey
);

As to the insert:

insert into table2 (column names)
select something 
from table1 
where not exists
(
  select *
  from table2 
  where table2.somekey = table1.somekey
);