通過()進行聚合與沒有值聚合或恆定值相同。 例如:
create table test_group(cod varchar2(16), descr varchar2(16), num number);
insert into test_group values ('a', 'letter A', 10);
insert into test_group values ('b', 'letter b', 20);
insert into test_group values ('b', 'letter B', 35);
insert into test_group values ('c', 'letter c', 70);
insert into test_group values ('c', 'letter c', 99);
聚集的任何值
SQL> select sum(num)
2 from test_group;
SUM(NUM)
----------
234
聚集的null
SQL> select sum(num)
2 from test_group
3 group by null;
SUM(NUM)
----------
234
聚集的()
:
SQL> select sum(num)
2 from test_group
3 group by();
SUM(NUM)
----------
234
聚集的恆定值:
SQL> select sum(num)
2 from test_group
3 group by 'constant';
SUM(NUM)
----------
234
你必須明確地寫你的彙集條件:
SQL> select *
2 from test_group
3 group by *;
group by *
*
ERROR at line 3:
ORA-00936: missing expression