How to count matching Sell-Orders for all Buy-Orders with dynamic attributes? – Mysql

I assume that the sell order id and buy order id is related. If not, then there is no relations in your data between sell and buy tables. You can try something like below to get the raw answer. First cte creates marker for all attributes. Second CTE gets all sales ids that fulfil all the attribute needs. Then final select gets the cases where buy orders are in line with sales attribute needs and price less than the buy order.

   with cte as ( 
select s.*
case
        when a.[attribute_id] = 'whatever attribute you choose' and a.value >= 'whatever the benchmark is' then 1
        when a.[attribute_id] = 'whatever 2nd attribute you choose' and a.value >= 'whatever the benchmark is' then 1
            else 0
            end as marker
    from [Sell Orders]  s
        inner join [Sell Order Attributes] a on s.id = a.sell_order_id
),

cte2 as (
select id , sum(marker)
from cte
group by id
having sum(marker) = 2 --however many attributes you are testing
)

select *
    from [Buy Orders] b on b.id = s.id
        inner join [Buy Order Attributes] c on b.id = c.buy_order_id
        inner join  cte2 t on t.id = b.id


        Where  t.price < b.price