Compare two SQL tables and return missing ids?

Question

I have two simple tables: (here only the "id" column)

table1:

id
1
2
3
4

table2:

id
2
4

the sql query should compare the two tables for missing "id" in table2 and return: 1,2

any ideas? :) TY

Answer 1

There are several ways to skin this cat:

SELECT    table1.ID
FROM      table1
WHERE     table1.ID NOT IN(SELECT table2.ID FROM table2)

Or you could use a left outer join:

SELECT          table1.ID
FROM            table1
LEFT OUTER JOIN table2 ON table1.ID = table2.ID
WHERE           table2.ID IS NULL

Answer 2

select t1.*
from table1 t1
left outer join table2 t2 on t1.id = t2.id
where t2.id is null

Answer 3

Try this:

SELECT    table1.id
FROM      table1
WHERE     table1.id NOT IN(SELECT table2.id FROM table2)