请教：分析函数问题

[wfeng7907]

请教：COUNT（*）over()和COUNT（*）over(ORDER BY COL)有什么区别？
COUNT（*）over()的用处是什么？

[沝林]

COUNT（*）over() 是计算所有记录条数，和COUNT（*）over(ORDER BY COL)差不多，唯一区别就是后者经过排序了,partition by col是按col分组，计算每组的count（*）
select a,COUNT（*）over() from t
a COUNT（*）over()
1 5
7 5
2 5
2 5
5 5
select a,COUNT（*）over(ORDER BY a) from t
a COUNT（*）over(ORDER BY a)
1 5
2 5
2 5
5 5
7 5

select a,COUNT（*）over(partition BY a) from t
a COUNT（*）over()
1 1
2 2
2 2
5 1
7 1

[沝林]

错了，不好意思，COUNT（*）over(ORDER BY a)应该是按a的顺序累计条数
select a,COUNT（*）over(ORDER BY a) from t
a COUNT（*）over(ORDER BY a)
1 1
2 3
2 3
5 4
7 5

[沝林]

select a,b,COUNT（*）over(partition by a ORDER BY b) from b
a b COUNT（*）over(partition by a ORDER BY b)
1 1 1
2 2 1
2 3 2
3 1 1
4 1 1
4 2 3
4 2 3
5 1 1

[wfeng7907]

COUNT（*）over(ORDER BY a)应该是按a的顺序累计条数，是不是指累计的是>=a的记录数？

[bzszp]

自己试一下就知道了

[沝林]

COUNT（*）over(ORDER BY a)应该是按a的顺序累计条数，是不是指累计的是>=a的记录数？
-------
是<=a的记录数吧

[wfeng7907]

明白了，多谢！！给分！