SELECT MIN(rowid), col1, col2
FROM t
GROUP BY col1, col2;

DELETE FROM t
WHERE rowid NOT IN (
SELECT MIN(rowid)
FROM t
GROUP BY col1, col2);

非常间洁，是我喜欢的风格，呵呵

下面是表的结构

CREATE TABLE t (
col1 VARCHAR2(3),
col2 VARCHAR2(3));

INSERT INTO t VALUES ('AAA', '123');
INSERT INTO t VALUES ('BBB', '123');
INSERT INTO t VALUES ('CCC', '789');
INSERT INTO t VALUES ('AAA', '123');
INSERT INTO t VALUES ('DDD', '123');
INSERT INTO t VALUES ('CCC', '789');
INSERT INTO t VALUES ('CCC', '987');

一眼看明！