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, TextI 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
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