Question

oracle 中，对指定的列值重复，只显示第一个值，其余列保持不变，要如何实现？高人赐教

表字段： A B C D
1 2 3 4
1 2 3 4
3 3 4 4
a b a b
a b c d
a b c d
对指定的列（如：A，B）进行处理，有重复的列值，只显示第一个的值，其余为空(“”)
结果如下：
表字段： A B C D
1 2 3 4
3 4
3 3 4 4
a b a b
c d
c d

Answer 1

通过脚本来实现，比较直观容易理解。
declare
v_a char(1):='0';
v_b char(1):='0';
v_aa char(1):='';
v_bb char(1):='';
cursor c1 is select A,B,C,D from TAB order by A,B,C,D;
v c1%rowtype;
begin
open c1;
loop
fetch c1 into v;
exit when c1%notfound;
if v_a=v.a then v_aa:='';
else v_a:=v.a; v_aa:=v.a;
end if;
if v_b=v.b then v_bb:='';
else v_b:=v.b; v_bb:=v.b;
end if;
dbms_output.put_line(v_aa||' '||v_bb||' '||v.c||' '||v.d);
end loop;
close c1;
end;

Answer 2

表名我为其命名为:a1

create view v_a1 as select rownum as rn,a1.* from a1;

select T.a,T.b,T.c,T.d
from (
select rn,a,b,c,d
from v_a1
where (rn,a,b) in (select min(rn) as rn,a,b
from v_a1
group by a,b)
union all
select rn,'' as a,'' as b,c,d
from v_a1 v1
where (rn,a,b) not in (select min(rn) as rn,a,b
from v_a1
group by a,b)
) T
order by T.rn;