--删除表中的重复记录。
create table user_info
(
username varchar2(20),
password varchar2(20)
)
insert into user_info values('JACK','123',SQ_USER.NEXTVAL);
insert into user_info values('JACK','123',SQ_USER.NEXTV);
insert into user_info values('SHININ','123',SQ_USER.NEXTVAL);
insert into user_info values('SHININ','123',SQ_USER.NEXTVAL);
insert into user_info values('SHININ','456',SQ_USER.NEXTVAL);
--方案一
CREATE TABLE USER_INFO2
AS
SELECT DISTINCT * FROM USER_INFO ;
DROP TABLE USER_INFO;
RENAME USER_INFO2 TO USER_INFO;
SELECT * FROM USER_INFO;
--方案二
ALTER TABLE USER_INFO ADD ID NUMBER;
CREATE SEQUENCE SQ_USER;
DELETE FROM USER_INFO;
DELETE FROM USER_INFO
WHERE ID NOT IN(
SELECT MIN(ID)AS ID FROM USER_INFO
GROUP BY (USERNAME,PASSWORD));