Open martianzhang opened 5 years ago
As this blog said
"varvhar等字段建立索引长度计算语句：select count(distinct left(test,5))/count(*) from table; 越趋近1越好"
count(distinct left(col, n)) more closed to count(distinct col) will be better.
Feature Description
As this blog said
"varvhar等字段建立索引长度计算语句：select count(distinct left(test,5))/count(*) from table; 越趋近1越好"
count(distinct left(col, n)) more closed to count(distinct col) will be better.