实现MySQL逗号数据计数

亮点:1、结合使用length()及replace(str,',','')来实现其计数功能;

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

            3、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

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