我如何只能从相同的 id_category 和 id_service 中获取具有最大日期的行

Question

我有这个 table:

id_category | id_service | amount | date

这个 table 有不止一行 id_category 和 id_service。我如何只能从相同的 id_category 和 id_service 中获取具有最大日期的行？

示例数据：

1 | 1 | 0.1  | 2015-05-05
1 | 1 | 0.12 | 2015-05-06
1 | 2 | 0.2  | 2015-05-04
1 | 2 | 0.25 | 2015-05-05
1 | 2 | 0.30 | 2015-05-06
2 | 1 | 0.15 | 2015-05-05

我想得到这个结果：

1 | 1 | 0.12 | 2015-05-06
1 | 2 | 0.30 | 2015-05-06
2 | 1 | 0.15 | 2015-05-05

谢谢！

Answer 1

http://sqlfiddle.com/#!9/ad96b/3

SELECT t1.* 
FROM t1
LEFT JOIN t1 t2
ON t1.id_category = t2.id_category
   AND t1.id_service = t2.id_service
   AND t1.`date` < t2.`date`
WHERE t2.date IS NULL

Answer 2

select id_category, id_service, max(amount), min(date)
from table_name
group by id_category, id_service;

Answer 3

也许你的查询是这样的

select a.* from table a
where a.date = 
(select max(b.date) from table b where a.id=b.id group by b.id_service, b.id_category)
group by a.id_category, a.id_service;

Answer 4

您可以使用派生 table 然后使用内部联接

MYSQL 版本 SQL FIDDLE

SELECT gd.*, t.amount
FROM (Select id_category, id_service, max(date) date
      FROM t
      group by id_category, id_service)  gd
INNER JOIN t ON gd.id_service = t.id_service 
                AND gd.id_category = t.id_category
                AND gd.date = t.date
ORDER BY gd.id_category, gd.id_service

MSSQL 版本：- 如果 SQL 服务器 SQLFIDDLE

，这将通过 CTE 获得

;WITH GroupedData AS
   (
       select id_category, id_service, max(date) date
       FROM t
       group by id_category, id_service       
   ) 
   SELECT gd.*, t.amount
   FROM GroupedData  gd
   INNER JOIN t ON gd.id_service = t.id_service 
                AND gd.id_category = t.id_category
                AND gd.date = t.date
   ORDER BY gd.id_category, gd.id_service

我如何只能从相同的 id_category 和 id_service 中获取具有最大日期的行

How I can get only row from same id_category and id_service with the max date of them

mysql

sql

group-by

max