数据按日期排正序，若有连续的col2，则取最小日期及col2显示
否则，显示日期和col2
表数据为:
2000/01/02 A
2000/04/01 A
2003/01/01 B
2004/02/03 B
2005/02/02 C
2006/01/01 A

SQL语句的结果为:
2000/01/02 A
2003/01/01 B
2005/02/02 C
2006/01/01 A

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【Solved By sonic】

SQL> SELECT * FROM ZTEST;

A B
--------------- ----------
2000-1-2 A
2000-4-1 A
2003-1-1 B
2004-2-3 B
2005-2-2 C
2006-1-1 A

6 rows selected

SQL> SELECT A, B
2 FROM (SELECT T.*,
3 LAG(T.A) OVER(ORDER BY T.A) PA,
4 LAG(T.B) OVER(ORDER BY T.A) PB
5 FROM ZTEST T) WHERE (PA <> A AND PB <> B) OR PA IS NULL
6 /

A B
--------------- ----------
2000-1-2 A
2003-1-1 B
2005-2-2 C
2006-1-1 A

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取连续数中的第一个

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