使用select from dual插入数据的区别

Question

what is the difference with both query ? are they same ? do they give the same results ? I saw them in a script and I wonder if there is a difference.

Query 1 :
insert into tab1 ( id , name , last ) values ( 1 , 'st' , 'ov');


Query 2 :
insert into tab1 ( id , name , last ) select 1 , 'st' , 'ov' from dual;

Answer 1

There is no difference in this case.

Using a select ... from dual for the insert can be useful in some cases (when using data from another table for example, an union , etc.), but in this case it doesn't add anything to the usual insert into .

Consider this being useful:

insert
into   table_x
( col1
)
select 'a'
from   dual
union
all
select 'b'
from   dual
;