ALL, SOME and subquery -A Test

SQL> select * from tab1;

         A          B          C
---------- ---------- ----------
         1          2          3
         2          2          3
         3          2          3
         4          4          3

SQL> select * from tab1 where a = (select a from tab1);
select * from tab1 where a = (select a from tab1)
                              *
ERROR at line 1:
ORA-01427: single-row subquery returns more than one row


SQL> select * from tab1 where a = all (select a from tab1);

no rows selected

SQL> select * from tab1 where a = some (select a from tab1);

         A          B          C
---------- ---------- ----------
         1          2          3
         2          2          3
         3          2          3
         4          4          3

SQL> select * from tab1 where a = all (select b from tab1);

no rows selected

SQL> select * from tab1 where a = some (select b from tab1);

         A          B          C
---------- ---------- ----------
         2          2          3
         4          4          3

SQL> select * from tab1 where a = all (select c from tab1);

         A          B          C
---------- ---------- ----------
         3          2          3

SQL> select * from tab1 where a = some (select c from tab1);

         A          B          C
---------- ---------- ----------
         3          2          3

SQL> select * from tab1 where a = some (select b, c from tab1);
select * from tab1 where a = some (select b, c from tab1)
                                   *
ERROR at line 1:
ORA-00913: too many values