Question

oracle查询语句过滤重复数据问题

oracle查询语句过滤重复数据问题，如下：字段名为x和y,表名为t
x y
a b
a c
a d
a b
a c
a d
请问如何查询能得到以下结果：
x y
a b
a c
a d
先谢过了

Answer 1

select distinct x,y ferom t;
select x,y from t group by x,y;
select * from t group by x,y having count(*)>1 ;--查出有重复记录的数据，如果having count(*)=1 是查出没有重复记录的数据
select * from t a1 where rowid=(select max(rowid) from t a2 where a2.x=a1.x and a2.y=a1.y); --利用rowid唯一，适用于少量重复数据
还有 rank over（partition）这个函数你也可以好好看哈哦

Answer 2

select distinct x, y from t;

Answer 3

第一种方式：
select distinct x, y from t;

第二种方式：
select x,y from t group by x,y

推荐第二种方式

Answer 4

select distinct x, y from t;
或者
select x,y from (select x,y,count(*) from t group by x,y) b;

Answer 5

select temp.x, temp.yfrom (
select t.x, t.y, row_number() OVER(PARTITION BY x ORDER BY t.y desc) as row_flg from t t ) tempwhere temp.row_flg = '1'