行のすべての列について、最小入札価格の副選択で内部結合を使用できます
select m.id, m.item_id, m.user_id, m.bid_price
from my_table m
inner join (
select item_id, min(id) min_id, min(bid_price) min_price
from my_table
where item_id IN (1,2,3)
group by item_id
) t on t.item_id = m.item_id
and t.min_price= m.bid_price
and t.min_id = m.id
または..floatデータ型がある場合は、unsignedにacstを使用できます
select m.id, m.item_id, m.user_id, cast(m.bid_price as UNSIGNED)
from my_table m
inner join (
select item_id, min(id) min_id, min(bid_price) min_price
from my_table
where item_id IN (1,2,3)
group by item_id
) t on t.item_id = m.item_id
and t.min_price= m.bid_price
and t.min_id = m.id