SQL语句分类变量计数与百分比统计

select reviewAverage,count(reviewAverage) as count from table_nm group by reviewAverage having reviewAverage is not null order by reviewAverage

简单的查询语句大家都比较容易的理解。select 字段A,count(A) as count from 表名 group by 字段A order by count。但是想要百分比出现在后面，需要子查询语句。

*select reviewAverage,count(reviewAverage) as count,concat(round(count(reviewAverage)/(select count(*) from 表名)100,2),’’,’%’) as per from 表名 group by reviewAverage having reviewAverage is not null order by reviewAverage

百分比=count/sum

count(字段)-----------计数count

select count() from 表名 ------- 求出sum

count(字段)/(select count() from 表名)---------百分比

round(百分比100，2）-------保留两位小数

concat(round(百分比100，2），‘’，’%’)-------转换成百分比

只需要把查询结果：concat(round(count(reviewAverage)/(select count() from 表名)100,2),’’,’%’) as per 当成一个字段即可。

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