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‘);

--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_2ORDER BY ID_2