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？

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

select Year as 年份

, 第一季度= sum(case Q when 0 then amount end)

, 第二季度= sum(case Q when 1 then amount end)

, 第三季度= sum(case Q when 2 then amount end)

, 第四季度= sum(case Q when 3 then amount end)

from (

select year(ShippedDate) as Y, month(ShippedDate) / 4 as Q,

UnitPrice*Quantity*(1-Discount) as amount

from Orders,[Order Details]

where Orders.OrderID=[Order Details].OrderID

and year(ShippedDate) is not null

group by year(ShippedDate) , month(ShippedDate) / 4

) as a

group by Y

order by Y

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