Table: buyers

+----------+---------+
| Column   | Type    |
+----------+---------+
| id       | int     |
| username | varchar |
+----------+---------+

id is the primary key.

Table: lots

+---------------+---------+
| Column        | Type    |
+---------------+---------+
| id            | int     |
| name          | varchar |
| starting_price| int     |
| bid_step      | int     |
+---------------+---------+

id is the primary key.

Table: bids

+-----------+------+
| Column    | Type |
+-----------+------+
| buyer_id  | int  |
| lot_id    | int  |
| time      | text |
+-----------+------+

(buyer_id, lot_id, time) identifies each bid.