Question

已知 ，数据库两个字段，年，月。现在要按照季度分组查询，怎么写sql语句？

Answer 1

先case when将月份变成季度，然后再group by即可，SQL如下：

select year, quarter, count(1)
from (
    select year,
        case
        when month < 4 then 1
        when month < 7 then 2
        when month < 10 then 3
        else 4
        end as quarter
    from table
) as result
group by year, quarter