insert 表(class,subclass) select A.class, B.subclass from (select distinct class from 表)A join (select 4 as subclass)B on 1>0
insert 表 select a.class(pk),b.subclass,a.content from 表 a inner join ( select class(pk),max(subclass)+1 as subclass from 表 group by class(pk) ) b on a.class(pk)=b.class(pk)
select A.class,
B.subclass
from (select distinct class from 表)A
join (select 4 as subclass)B on 1>0
select a.class(pk),b.subclass,a.content
from 表 a
inner join
(
select class(pk),max(subclass)+1 as subclass from 表 group by class(pk)
) b on a.class(pk)=b.class(pk)