Stuck in building MySQL query

Question

Given an example of table:

id | item_id | user_id | bid_price
----------------------------------

The task is to select rows wi

Answer 1

Use this query:

SELECT id, item_id, user_id, min(bid_price) as bid_price 
FROM YOUR_TABLE_NAME 
GROUP BY item_id;

Answer 2

For the all the columns in the rows you could use a inner join on subselect for min bid price

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

or .. if you have some float data type you could use a acst for unsigned

  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 

Answer 3

You can use MIN() with GROUP BY in the query:

SELECT id, item_id, MIN(bid_price) AS min_bid, user_id 
FROM your_tbl 
GROUP BY item_id 
HAVING item_id in(1, 2, 3);