預先準備

create table p(
       name varchar2(10)
);

insert into p values(‘黃偉福‘);
insert into p values(‘趙洪‘);
insert into p values(‘楊華‘);

每條語句執行三次插入

select rowid,p.* from p;

select distinct * from p;

查詢最小rowID，只返回了一條數據

select min(rowid) from p p1 where p1.name = p1.name

查詢每個重復名字的最小rowID，註意子查詢返回的是3條數據，並不是一條，思考一下具體執行順序

select rowid,p1.* from p p1 where rowid = (select min(rowid) from p p2 where p1.name = p2.name);

刪除重復數據，只保存數據中的最小rowID ，然後查詢

delete from p p1 where rowid > (select min(rowid) from p p2 where p1.name = p2.name);
select rowid,p.*
 
 from p;

select from 具體執行