关于SQL case when的用法介绍

sql case when 用法

主要是给变量赋值，将连续型变量离散化，主要用sql中的case when

实例：

create table table_name_new as ----将时间离散化为时间段，并创建一个新表table_name_new

select * ,

case

when call_period >= '00' and call_period < '08' then 'period_1'

when call_period >= '08' and call_period < '11' then 'period_2'

when call_period >= '11' and call_period < '13' then 'period_3'

when call_period >= '13' and call_period < '17' then 'period_4'

when call_period >= '17' and call_period < '19' then 'period_5'

when call_period >= '19' and call_period < '24' then 'period_6'

else null end time_period

from table_name -- 原表