批量和出价的 SQL 查询：查找用户是否有最高出价答案

【问题标题】：SQL query for lots and bids: finding if user has highest bid批量和出价的 SQL 查询：查找用户是否有最高出价
【发布时间】：2016-06-09 21:24:14
【问题描述】：

我正在构建一个 Laravel 拍卖应用程序。我有一张拍手表和一张出价表。

手数表：

mysql> select id, lot_name, created_at, updated_at from lots;
+----+----------+---------------------+---------------------+
| id | lot_name | created_at          | updated_at          |
+----+----------+---------------------+---------------------+
|  1 | Lot 1    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  2 | Lot 2    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  3 | Lot 3    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  4 | Lot 4    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  5 | Lot 5    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  6 | Lot 6    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  7 | Lot 7    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  8 | Lot 8    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
|  9 | Lot 9    | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 10 | Lot 10   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 11 | Lot 11   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 12 | Lot 12   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 13 | Lot 13   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 14 | Lot 14   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 15 | Lot 15   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
| 16 | Lot 16   | 2016-06-09 14:23:58 | 2016-06-09 14:23:58 |
+----+----------+---------------------+---------------------+

和出价表：

mysql> select * from bids;
+----+--------+---------+-----------+---------------------+---------------------+
| id | lot_id | user_id | bid_value | created_at          | updated_at          |
+----+--------+---------+-----------+---------------------+---------------------+
|  1 |      1 |       2 | 100       | 2016-06-01 11:14:15 | 2016-06-09 14:23:59 |
|  2 |      1 |       2 | 150       | 2016-06-01 13:19:02 | 2016-06-09 14:23:59 |
|  3 |      1 |       3 | 160       | 2016-06-02 09:02:35 | 2016-06-09 14:23:59 |
|  4 |      1 |       2 | 180       | 2016-06-02 12:25:16 | 2016-06-09 14:23:59 |
|  5 |      2 |       2 | 100       | 2016-06-01 09:26:17 | 2016-06-09 14:23:59 |
|  6 |      2 |       3 | 150       | 2016-06-01 10:14:15 | 2016-06-09 14:23:59 |
|  7 |      2 |       2 | 160       | 2016-06-01 11:35:09 | 2016-06-09 14:23:59 |
|  8 |      3 |       3 | 180       | 2016-06-04 11:14:15 | 2016-06-09 14:23:59 |
|  9 |      1 |       3 | 200       | 2016-06-03 19:29:56 | 2016-06-09 14:23:59 |
| 10 |      3 |       2 | 250       | 2016-06-04 23:14:15 | 2016-06-09 14:23:59 |
| 11 |      4 |       2 | 500       | 2016-06-03 09:16:39 | 2016-06-09 14:23:59 |
| 12 |      1 |       3 | 230       | 2016-06-01 11:14:15 | 2016-06-09 14:23:59 |
| 13 |      1 |       2 | 250       | 2016-06-01 11:14:15 | 2016-06-09 14:23:59 |
| 14 |      3 |       2 | 300       | 2016-06-05 02:14:15 | 2016-06-09 14:23:59 |
| 15 |      2 |       3 | 180       | 2016-06-01 20:44:15 | 2016-06-09 14:23:59 |
| 16 |      4 |       2 | 600       | 2016-06-04 08:59:15 | 2016-06-09 14:23:59 |
| 17 |      1 |       3 | 300       | 2016-06-03 17:20:30 | 2016-06-09 14:23:59 |
| 18 |      1 |       3 | 350       | 2016-06-04 18:04:55 | 2016-06-09 14:23:59 |
| 19 |      7 |       2 | 160       | 2016-06-02 22:24:02 | 2016-06-09 14:23:59 |
| 20 |      1 |       3 | 400       | 2016-06-05 07:00:27 | 2016-06-09 14:23:59 |
| 21 |      8 |       3 | 100       | 2016-06-02 11:58:29 | 2016-06-09 14:23:59 |
| 22 |      1 |       3 | 450       | 2016-06-05 10:09:06 | 2016-06-09 14:23:59 |
| 23 |      1 |       2 | 480       | 2016-06-05 14:12:15 | 2016-06-09 14:23:59 |
| 24 |      5 |       2 | 1000      | 2016-06-02 13:38:34 | 2016-06-09 14:23:59 |
| 25 |      1 |       2 | 525       | 2016-06-05 20:39:29 | 2016-06-09 14:23:59 |
| 26 |      1 |       3 | 600       | 2016-06-05 23:59:50 | 2016-06-09 14:23:59 |
| 27 |      6 |       2 | 1000      | 2016-06-01 07:00:02 | 2016-06-09 14:23:59 |
| 28 |      6 |       3 | 1200      | 2016-06-04 23:14:56 | 2016-06-09 14:23:59 |
+----+--------+---------+-----------+---------------------+---------------------+

Relation Lot-Bid：一个批次可以包含多个出价（来自多个用户），每个出价只属于一个批次和一个用户。

我的目标是创建一个视图，显示用户是否对给定批次的出价最高。我将在一个带有绿色/红色行颜色的表格中指出这一点（绿色是用户对该批次的最高出价）。

理想情况下，我想实现以下目标（这样我就可以创建一个 Laravel 查询并将其发送到视图以循环遍历数组）

+--------+---------+----------------+----------------+
| lot_id | user_id | max(bid_value) | highest value  |  extra columns from the lots table such as created_at, updated_at
+--------+---------+----------------+----------------+
|      1 |     2   |     525        |    600         |   ....
|      2 |     2   |     160        |    180         |   ....
|      3 |     2   |     300        |    300         |   ....
|      4 |     2   |     600        |    600         |   ....
|      5 |     2   |     1000       |    1000        |   ....
|      6 |     2   |     1000       |    1200        |   ....
|      7 |     2   |     160        |    160         |   ....
+--------+--------------------------+----------------+

我得到以下内容：

mysql> select lot_id, max(bid_value) as 'highest value' from bids group by lot_id;
+--------+---------------+
| lot_id | highest value |
+--------+---------------+
|      1 | 600           |
|      2 | 180           |
|      3 | 300           |
|      4 | 600           |
|      5 | 1000          |
|      6 | 1200          |
|      7 | 160           |
|      8 | 100           |
+--------+---------------+

到：

mysql> select lot_id, max(bid_value) as user_highest_bid from bids where user_id=2 group by lot_id;
+--------+------------------+
| lot_id | user_highest_bid |
+--------+------------------+
|      1 | 525              |
|      2 | 160              |
|      3 | 300              |
|      4 | 600              |
|      5 | 1000             |
|      6 | 1000             |
|      7 | 160              |
+--------+------------------+

我如何结合这些来获得我想要的表格，因此包括额外的批次信息，并且只包含用户出价的这些批次？

---- 编辑 ---- 添加来自 Mureinik 的正确答案（稍作改动）：

mysql> SELECT lots.*, b.*
    ->        FROM   lots
    ->        JOIN   (SELECT   lot_id,
    ->                         2 AS user_id,
    ->                         MAX(bid_value) AS highest_value,
    ->                         MAX(CASE user_id WHEN 2 THEN bid_value END) AS highest_bid
    ->                FROM     bids
    ->                GROUP BY lot_id) b ON lots.id = b.lot_id AND highest_bid IS NOT NULL;

【问题讨论】：

标签： mysql sql select eloquent

【解决方案1】：

您需要在这里进行两个查询 - 一个查询批次的详细信息，另一个查询汇总出价。这里有一个巧妙的技巧是使用 case 语句来表示某个用户的最高出价，因此您只需要一个聚合查询。

在此查询中，我假设您只想要用户实际出价的结果。如果这不是真的，只需在连接中删除not null 条件：

SELECT lot.*, b.*
FROM   lots
JOIN   (SELECT   lot_id, 
                 2 AS user_id, 
                 MAX(bid_value) AS highest_value,
                 MAX(CASE user_id WHEN 2 THEN bid_value END) AS highest_bid
        FROM     bids
        GROUP BY lot_id) b ON lot.lot_id = b.lot_id AND highest_bid IS NOT NULL

【讨论】：

这很棒！非常感谢。我做了一些较小的更改并编辑了上面的问题以包含带有小修正的版本