Question

I want to check if the OrderID = 2 exist in Table1 and does not exist in Table2 then return 1 or true.

If OrderID = 2 exist in both table then return 0 or false..

How can that be done in SQL query?

Table1
=======
ID | OrderID
1    2
2    2

Table2
======
OrderID | Name
1         A
2         B

Answer 1

Something like that?

select ID,t1.OrderID, t2.OrderID is null as notinboth
from table1 as t1 left join table2 as t2 using (OrderID);