不使用分析函式計算每個月每種車型銷售前3的行
create view test_sale asselect '2019-01' as order_date,'a' as brand_id ,10 as cnt from dual union all
select '2019-01' as order_date,'b' as brand_id ,20 as cnt from dual union all
select '2019-01' as order_date,'c' as brand_id ,30 as cnt from dual union all
select '2019-01' as order_date,'d' as brand_id ,15 as cnt from dual union all
select '2019-01' as order_date,'e' as brand_id ,22 as cnt from dual union all
select '2019-02' as order_date,'a' as brand_id ,10 as cnt from dual union all
select '2019-02' as order_date,'b' as brand_id ,30 as cnt from dual union all
select '2019-02' as order_date,'c' as brand_id ,30 as cnt from dual union all
select '2019-02' as order_date,'d' as brand_id ,15 as cnt from dual union all
select '2019-02' as order_date,'e' as brand_id ,22 as cnt from dual ;
自關聯,使用月份關聯,關聯後,匹配當前月銷售量比本車型銷售量大的資料。
彙總後,行數最少的,就是銷售量最多的。
select a.order_date, a.brand_id, a.cnt, count(*) as rnfrom test_sale a
join test_sale b
on a.order_date = b.order_date
and a.cnt <= b.cnt
group by a.order_date, a.brand_id, a.cnt;
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