SQL:1999

唯一约束

  1. select max(id),class 
  2. from student 
  3. group by class;

any_value

#不符合要求，不能保证any_value能够取到正确的值
select any_value(id),any_value(name),class,max(age)
from student 
group by class;

嵌套查询

select s2.* 
from(
  select class, max(age)
  from student 
  group by class
) as s1
join student s2 
on s1.class = s2.class and s1.age = s2.age

with as

with max_age as (
  select class, max(age) `age`
  from student
  group by class
)
select s.*
from max_age ma
join student s 
on ma.class = s.class and ma.age = s.age