我正在尝试选择卖家分组的COUNT(*)及其最新产品及其添加日期。但是,出于某种原因,它似乎按创建日期继续订购交易,即使我尝试子查询以防止这种情况也会提升。这是一个示例表:
------------------------------------------------
| ID | Provider | URL | CreateDate |
------------------------------------------------
| 1 | Prov1 | http://ex.com/1 | 2015-05-10 |
| 2 | Prov1 | http://ex.com/2 | 2015-06-10 |
| 3 | Prov1 | http://ex.com/3 | 2015-07-10 |
| 4 | Prov2 | http://ex.com/4 | 2015-05-10 |
| 5 | Prov2 | http://ex.com/5 | 2015-06-10 |
------------------------------------------------
我希望返回以下内容:
-----------------------------------------------------------
| ID | COUNT(*) | Provider | URL | CreateDate |
-----------------------------------------------------------
| 3 | 3 | Prov1 | http://ex.com/3 | 2015-07-10 |
| 5 | 2 | Prov2 | http://ex.com/5 | 2015-06-10 |
-----------------------------------------------------------
我目前的查询是:
SELECT ID,COUNT(*),Provider,CreateDate,URL
FROM (SELECT * FROM products ORDER BY CreateDate DESC)
GROUP BY Provider;
但这似乎不起作用。有没有人有建议?
修改 谢谢大家的答案。对我来说非常奇怪的是,虽然它们似乎在SQL小提琴中工作,但它们在我的数据库服务器上失败了。例如,在服务器上使用以下内容提供以下内容:
mysql> INSERT INTO products
-> (`ID`, `Provider`, `URL`, `CreateDate`)
-> VALUES
-> (1, 'Prov1', 'http://ex.com/1','2015-05-10'),
-> (2, 'Prov1', 'http://ex.com/2','2015-06-10'),
-> (3, 'Prov1', 'http://ex.com/3','2015-07-10'),
-> (4, 'Prov2', 'http://ex.com/4','2015-05-10'),
-> (5, 'Prov2', 'http://ex.com/5','2015-06-10')
-> ;
Query OK, 5 rows affected (0.06 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql> SELECT ID,COUNT(*),Provider,CreateDate,URL
-> FROM (SELECT * FROM products ORDER BY CreateDate DESC) t1
-> GROUP BY Provider;
+------+----------+----------+---------------------+-----------------+
| ID | COUNT(*) | Provider | CreateDate | URL |
+------+----------+----------+---------------------+-----------------+
| 1 | 3 | Prov1 | 2015-05-10 00:00:00 | http://ex.com/1 |
| 4 | 2 | Prov2 | 2015-05-10 00:00:00 | http://ex.com/4 |
+------+----------+----------+---------------------+-----------------+
虽然在SQL小提琴上运行相同的东西按预期工作。此外,关于JOIN的评论应该有效,但我遇到同样的问题,它会返回意外的结果。我的MySQL版本是5.5.37-MariaDB-34.0。关于这个的任何想法?
答案 0 :(得分:0)
SELECT p1.*, COUNT(*)
FROM products p1
JOIN
(
select provider, max(CreateDate) as m_date
from products
group by provider
) p2 on p1.provider = p2.provider and p1.CreateDate = p2.m_date
答案 1 :(得分:0)
您需要指定希望mysql返回计数内容的字段名称:
select count(*) as nro from table;
在你的情况下:
SELECT ID,COUNT(*) as nro,Provider,CreateDate,URL
FROM (SELECT * FROM products ORDER BY CreateDate DESC)
GROUP BY Provider;
但是对于所有解决方案,您需要为此部分查询创建别名" SELECT * FROM products ORDER BY CreateDate DESC"
CREATE VIEW p AS (SELECT * FROM products ORDER BY CreateDate DESC);
和第二个查询:
SELECT ID,COUNT(*) as nro,Provider,CreateDate,URL
FROM (p)
GROUP BY Provider;
必须工作。
答案 2 :(得分:0)
我是在SQL Server中完成的,但mysql中的查询有效。
Create TABLE #Products(
Id int,
Provider varchar(50),
URL Varchar(300),
Createdate varchar(50)
)
INSERT INTO #Products
SELECT 1,'Prov1','http://ex.com/1 ','2015-05-10' UNION ALL
SELECT 2,'Prov1','http://ex.com/2 ','2015-06-10' UNION ALL
SELECT 3,'Prov1','http://ex.com/3 ','2015-07-10' UNION ALL
SELECT 4,'Prov2','http://ex.com/4 ','2015-05-10' UNION ALL
SELECT 5,'Prov2','http://ex.com/5 ','2015-06-10'
SELECT p1.id, p2.Provider,p2.m_date,p1.url, COUNT(*)
FROM #products p1
JOIN
(
select provider, max(CreateDate) as m_date
from #products
group by provider
) p2 on p1.provider = p2.provider and p1.CreateDate = p2.m_date
GROUP BY p1.id, p2.Provider,p2.m_date,p1.url