SQL & PL/SQL

Hello Everyone,

DB: 10g.

Problem: I have two tables - A and B. Both have ID as column which is a primary key of the tables. A and B got records from table C.

SQL> SELECT COUNT(*) FROM A;
816234
SQL> SELECT COUNT(ID) FROM A;
816234

SQL> SELECT COUNT(*) FROM B;
750878
SQL> SELECT COUNT(ID) FROM B;
750878

SQL> SELECT 816234 - 750878 FROM dual;
65356

SQL>select count(id) from A where id not in (select id from B);
65690 Why not 65356?

SQL>select id from A minus select id from B;
65960 rows. How come?

Please advice.

Thanks.