Sql COUNT性能问题(Sql COUNT Performance Question)

Sql COUNT性能问题(Sql COUNT Performance Question)

示例表的结构：

Id, Integer (PK) Name, Varchar(100) Description, Text

我需要知道以下两者之间是否存在性能差异：

SELECT COUNT(*) FROM Example;

和

SELECT COUNT(Id) FROM Example;

或者不存在差异？

Structure of Example table:

Id, Integer (PK) Name, Varchar(100) Description, Text

I need to know if exists difference in performance between:

SELECT COUNT(*) FROM Example;

and

SELECT COUNT(Id) FROM Example;

Or does not exists differences?

最满意答案

性能和实际结果集都存在差异

COUNT SQL函数的性能

Differences exist in both performance and the actual resultset

Performance of COUNT SQL function