单选题

create table counttest(name char(1), ...

Question

create table counttest(name char(1), age char(2))

insert into counttest(name, age)

values('a','14'),

('a','15'),

('a','15'),

('b',NULL),

('b','16'),

('c','17'),

('d',null),

('e','')

select name, count(1),count(*),count(age), count(distinct(age))

from counttest 

group by name   

查询结果是

A. a 3 3 3 2<br>b 2 1 1 1<br>c 1 1 1 1<br>d 1 1 0 0<br>e 1 1 1 1

B. a 3 3 3 2<br>b 2 1 2 2<br>c 1 1 1 1<br>d 1 1 1 1<br>e 1 1 1 1

C. a 3 3 3 2<br>b 2 1 1 2<br>c 1 1 1 1<br>d 1 1 0 1<br>e 1 0 1 1

D. a 3 3 3 2<br>b 2 2 1 1<br>c 1 1 1 1<br>d 1 1 0 0<br>e 1 1 1 1