insert into table without the intersection part

Question

In case I have two SQL tables ,table_a and table_b, both are same , except they may contain different data, I want to insert into the table_b all the rows from table_b that does not exist in table_a already, how should the query look like ? The tables contain id1 and id2 columns only. Please tell me if my question is not clear

Insert into table_a ...

Thank you

Answer 1

; with cte_left as
(
select id1+id2
from table_a
where id1+id2 not in (select id1+id2 from table_b)
)

insert into table_b
select * from cte_left

Answer 2

You could use the EXCEPT operator:

INSERT INTO table_a (id1, id2)
SELECT id1, id2
FROM (
  SELECT id1, id2
  FROM table_b

  EXCEPT

  SELECT id1, id2
  FROM table_a
) except_gry

SQL Fiddle demo here

Answer 3

Insert into table_a ( id1, id2 ) 
select b.id1, b.id2
from table_b b
left outer join table_a a on a.id1 = b.id1 and a.id2 = b.id2
where a.id1 is null

Answer 4

You can use not exist in your query:

insert into table_a(id1,id2)
select id1,id2 
from table_b 
where not exists(select id1,id2 from table_a)