hive中的OVER从句

1、使用标准的聚合函数COUNT、SUM、MIN、MAX、AVG

2、使用PARTITION BY语句，使用一个或者多个原始数据类型的列

3、使用PARTITION BY与ORDER BY语句，使用一个或者多个数据类型的分区或者排序列

4、使用窗口规范，窗口规范支持以下格式：

(ROWS | RANGE) BETWEEN (UNBOUNDED | [num]) PRECEDING AND ([num] PRECEDING | CURRENT ROW | (UNBOUNDED | [num]) FOLLOWING)
(ROWS | RANGE) BETWEEN CURRENT ROW AND (CURRENT ROW | (UNBOUNDED | [num]) FOLLOWING)
(ROWS | RANGE) BETWEEN [num] FOLLOWING AND (UNBOUNDED | [num]) FOLLOWING123

当ORDER BY后面缺少窗口从句条件，窗口规范默认是 RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW.

当ORDER BY和窗口从句都缺失, 窗口规范默认是 ROW BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING.

OVER从句支持以下函数， 但是并不支持和窗口一起使用它们。

Ranking函数: Rank, NTile, DenseRank, CumeDist, PercentRank.

Lead 和 Lag 函数.