网友问我的：请教；我有这样一组数据
a 1 2 3
a 4 5 6
b 1 2 3
b 4 5 6
写一条SQL查出
a组第三列最大的
b组第三列最大的

我的实验如下：

SQL> create table tab1222(a varchar2(10),n1 number,n2 number,n3 number);

Table created.

SQL> insert into tab1222 values('a',1,2,3);

1 row created.

SQL> insert into tab1222 values('a',4,5,6);

1 row created.

SQL> insert into tab1222 values('b',1,2,3);

1 row created.

SQL> insert into tab1222 values('b',4,5,6);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from tab1222;

A     N1       N2  N3
---------- ---------- ---------- ----------
a      1        2   3
a      4        5   6
b      1        2   3
b      4        5   6

SQL> select a,max(n3) from tab1222 group by a;

A       MAX(N3)
---------- ----------
a      6
b      6

SQL> select * from tab1222  where n3 in (select a,max(n3) from tab1222 group by a);
select * from tab1222  where n3 in (select a,max(n3) from tab1222 group by a)
                                    *
ERROR at line 1:
ORA-00913: too many values

SQL>  select * from tab1222 tab1,(select a,max(n3) n3 from tab1222 group by a) tab2 where tab1.a=tab2.a and tab1.n3=tab2.n3;

A     N1       N2  N3 A         N3
---------- ---------- ---------- ---------- ---------- ----------
a      4        5   6 a   6
b      4        5   6 b   6

SQL>  select  tab1.a a,tab1.n1 n1,tab1.n2 n2,tab1.n3 n3 from tab1222 tab1,(select a,max(n3) n3 from tab1222 group by a) tab2 where tab1.a=tab2.a and tab1.n3=tab2.n3;

A     N1       N2  N3
---------- ---------- ---------- ----------
a      4        5   6
b      4        5   6

OK，完成