Oracle分组后取每组第一条

数据格式：

[img]https://img-blog.csdn.net/20130722152738875?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvcTQxMDA1NTk1NA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast[/img]

分组取第一条的效果：

[img]https://img-blog.csdn.net/20130722152855703?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvcTQxMDA1NTk1NA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast[/img]

[b][color=red]SQL:[/color][/b]

SELECT * FROM (
 SELECT ROW_NUMBER() OVER(PARTITION BY x ORDER BY y DESC) rn,       
        t.*       
        FROM test1 t
) WHERE rn = 1;

转载自：[url]http://www.cnblogs.com/dyllove98/archive/2013/07/22/3206423.html[/url]