实现MySQL逗号数据计数

亮点：一、结合使用length（）及replace(str,',','')来实现其计数功能；

           二、温故而知新，sum,   对比count 和sum

            三、嵌套查询格式书写漂亮，一方面便于养成Python书写习惯，同时，便于排查错误。

 

附代码：

select sum(case when num = 1 then 1 else 0 end) sum1,
       sum(case when num = 2 then 1 else 0 end) sum2,
       sum(case when num = 3 then 1 else 0 end) sum3,
       sum(case when num = 4 then 1 else 0 end) sum4,
       sum(case when num = 5 then 1 else 0 end) sum5,
       sum(case when num >5 then 1 else 0 end) other

 from(
    select length(iterm)-length(replace(iterm,',',''))+1  as num
    from database.table
) A
备注：iterm为字段名