CREATE TABLE DataInfo(

ID_1 VARCHAR(10),

ID_2 VARCHAR(10)

)

INSERT INTO DataInfo VALUES('A','Oracle');

INSERT INTO DataInfo VALUES('B','sqlserver');

INSERT INTO DataInfo VALUES('C','DB2');

INSERT INTO DataInfo VALUES('DB2','C');

INSERT INTO DataInfo VALUES('Oracle','A');

INSERT INTO DataInfo VALUES('sqlserver','B');

2.SQL查询

--删除重复数据

DELETE FROM DataInfo A WHERE EXISTS (SELECT 1 FROM DataInfo B WHERE A.ID_1=B.ID_2 AND A.ID_2=B.ID_1)

AND A.ID_1>A.ID_2

ORDER BY ID_2