如何删除数据表中重复列？
表T中字段A有重复的，也就是>1，现在想只保留一列，其中字段B是唯一的，可以比较大小，留B字段大的一条。

[解决办法]
要删除某字段，要看数据库是否支持，有不少数据库不支持删除字段。

alter table [table_name] drop column [column_name]
[解决办法]
oracle版本

SQL code

create table test (col_a number,col_b number);insert into test values(1,1);insert into test values(1,2);insert into test values(1,3);insert into test values(2,4);insert into test values(2,5);select AA.*  from test AA,       (select col_a, max(col_b) col_b          from test         where col_a in               (select col_a                  from (select col_a, count(distinct col_b)                          from test                         group by col_a                        having count(distinct col_b) > 1) temp)         group by col_a) tt where AA.col_a = tt.col_a   and AA.col_b < tt.col_b;
[解决办法]
看来又理解错了，楼主是要删除重复记录。总是被你的删除重复列给弄晕了，如下：
SQL code
Delete From T Where (a, b) NOT IN (Select A, max(B) as B From T Group By A)