mod()

一、通过Mod()判断奇数偶数

select 
(
    case
    when mod(id,2)=0 then id -1
    when mod(id,2)=1 and id = (select count(id) from seat) then id
    when mod(id,2)=1  then id+1
    end
)
as id, student
from seat 
order by id