--建表
create table tn(A int,B int,C int);
insert into tn select 1, 2, 4 from dual
union all select
1, 2, 3
from dual
union all select
2 ,3, 4
from dual
union all select
3 ,3, 5
from dual;
create table tn(A int,B int,C int);
insert into tn select 1, 2, 4 from dual
union all select
1, 2, 3
from dual
union all select
2 ,3, 4
from dual
union all select
3 ,3, 5
from dual;
表是和数据字段对应的一个表