Question

根据下面的表格和数据，我尝试获得的最高effective_from值小于当前时间戳，每个唯一的brand / model组合 - 实际上是当前价格项目

CREATE TABLE things
(`id` int, `brand` varchar(1), `model` varchar(5), `effective_from` int, `price` int);

INSERT INTO things
(`id`, `brand`, `model`, `effective_from`, `price`)
VALUES
(1, 'a', 'red', 1402351200, 100),
(2, 'b', 'red', 1402351200, 110),
(3, 'a', 'green', 1402391200, 120),
(4, 'b', 'blue', 1402951200, 115),
(5, 'a', 'red', 1409351200, 150),
(6, 'a', 'blue', 1902351200, 140),
(7, 'b', 'green', 1402358200, 135),
(8, 'b', 'blue', 1902358200, 155),
(9, 'b', 'red', 1902751200, 200),
(10, 'a', 'red', 1908351200, 210),
(11, 'a', 'red', 1402264800, 660);

到目前为止，当我为特定brand / model组合添加条件时，我已设法获取我要查找的行，但不知道如何获取所有独特行组合的当前价格。

SELECT *
FROM things
WHERE effective_from<UNIX_TIMESTAMP()
AND brand='a'
AND model='red'
ORDER BY effective_from DESC
LIMIT 1;

如果当前时间戳为1402404432，则结果应如下所示：

(1, 'a', 'red', 1402351200, 100),
(3, 'a', 'green', 1402391200, 120),
(2, 'b', 'red', 1402351200, 110),
(7, 'b', 'green', 1402358200, 135),

Answer 1

我猜你是在这之后。建议否则......

SELECT x.*
  FROM things x
  JOIN 
     ( SELECT brand
            , model
            , MAX(effective_from) max_effective_from 
         FROM things 
        WHERE effective_from <= UNIX_TIMESTAMP() 
        GROUP 
           BY brand
            , model
     ) y 
    ON y.brand = x.brand 
   AND y.model = x.model 
   AND y.max_effective_from = x.effective_from;
+------+-------+-------+----------------+-------+
| id   | brand | model | effective_from | price |
+------+-------+-------+----------------+-------+
|    1 | a     | red   |     1402351200 |   100 |
|    2 | b     | red   |     1402351200 |   110 |
|    3 | a     | green |     1402391200 |   120 |
|    7 | b     | green |     1402358200 |   135 |
+------+-------+-------+----------------+-------+

SELECT UNIX_TIMESTAMP();
+------------------+
| UNIX_TIMESTAMP() |
+------------------+
|       1402404432 |
+------------------+

选择具有最大值的唯一行（具有条件）

1 个答案: