SQL query to find record with ID not in another table

Question

I have two tables with binding primary key in database and I desire to find a disjoint set between them. For example,

• Table1 has columns (ID

Answer 1

SELECT COUNT(ID) FROM tblA a
WHERE a.ID NOT IN (SELECT b.ID FROM tblB b)    --For count


SELECT ID FROM tblA a
WHERE a.ID NOT IN (SELECT b.ID FROM tblB b)    --For results