标签：div mamicode inf ble null sel sql utf8 key
累加
先上表结构：
CREATE TABLE `abc` ( `jidu` int(11) NOT NULL AUTO_INCREMENT, `jine` int(11) DEFAULT NULL, PRIMARY KEY (`jidu`) ) ENGINE=InnoDB AUTO_INCREMENT=14270 DEFAULT CHARSET=utf8;
数据：
INSERT INTO `abc` (`jidu`, `jine`) VALUES (‘1‘, ‘100‘); INSERT INTO `abc` (`jidu`, `jine`) VALUES (‘2‘, ‘200‘); INSERT INTO `abc` (`jidu`, `jine`) VALUES (‘3‘, ‘300‘); INSERT INTO `abc` (`jidu`, `jine`) VALUES (‘4‘, ‘300‘);
想要的结果为季度金额的累加值：
这里利用错位自关联来实现，先看关联效果
select * from abc a JOIN abc b ON a.jidu >= b.jidu;
下面就好办了，实现语句为：
select a.jidu,a.jine,sum(b.jine) as leiji from abc a JOIN abc b ON a.jidu >= b.jidu GROUP BY a.jidu ORDER BY jidu;
累减
还是上面那个表，要的结果为每季度的金额差额：
还是自关联，先看关联效果：
select * from abc a left JOIN abc b ON a.jidu = b.jidu+1 ORDER BY a.jidu;
实现的sql：
select a.jidu,a.jine,ifnull(a.jine-b.jine,a.jine) as cha from abc a left JOIN abc b ON a.jidu = b.jidu+1 ORDER BY a.jidu;
完事，如有不对的地方请指正。
标签：div mamicode inf ble null sel sql utf8 key
原文地址：https://www.cnblogs.com/wangb2/p/12125334.html
