取排名前50%的数据

    SELECT
        goods_id,
        mall_id,
        gmv
    FROM(
        SELECT
            goods_id,
            mall_id,
            gmv,
            dense_rank() over (partition by mall_id order by gmv desc ) as dr_desc,
            dense_rank() over (partition by mall_id order by gmv ) as dr_asc
        FROM(
            SELECT
                goods_id,
                mall_id,
                SUM(amt) as gmv
            FROM
                table
            WHERE
                pt <= '2021-05-01'
                AND pt > date_sub('2021-05-01',7)
            GROUP BY 
                goods_id,
                mall_id
            HAVING
                SUM(amt) > 0
            )t11 
        )t12 
    WHERE
        dr_desc >= (dr_asc+dr_desc)/2    ---- 取gmv排序前50%的品