Question

我想仅针对所有项目获取最新报告，但仅针对每个item_id仅最新报告。这是我目前的解决方案：

SELECT distinct * FROM t.reports ORDER BY created DESC LIMIT 100

我的表格包含以下列：

id | user | item_id |  created
'2', '1',   '2643',  '2017-06-13 16:28:34'
'3', '1',   '19333', '2017-06-13 19:26:56'
'4', '1',   '19333', '2017-06-13 19:29:24'
'5', '1',   '1319',  '2017-06-13 19:29:56'
'6', '1',   '1319',  '2017-06-13 19:30:16'
'7', '1',   '1319',  '2017-06-13 19:30:17'
'8', '1',   '1319',  '2017-06-13 19:30:18'
'9', '1',   '1319',  '2017-06-13 19:30:25'
'10','1',   '1319',  '2017-06-13 19:31:51'

我希望没有重复的item_ids，只有该项目的最新条目。但我也想要所有报告，但没有重复的项目报告！

实施例：我希望当我执行我的查询时，我只返回第2,4和10行。

Answer 1

试试这个：

select a.id,a.user,a.item_id,a.created
from reports as a
where a.created=(select max(created) 
                from reports as b
                where a.item_id=b.item_id)

Answer 2

您可以使用group by：

SELECT * FROM t.reports WHERE created IN (SELECT max(created) FROM t.reports) 
GROUP BY item_id
LIMIT 100

Answer 3

试试这个我在测试数据库上测试过它：

SELECT DISTINCT item_id, MAX(created), id, user
FROM `t.reports`
GROUP BY item_id
ORDER BY MAX(created) DESC

Answer 4

试试这个让我知道这是否有效。

SELECT * 
FROM t.reports 
where item_id in (
                    select distinct item_id 
                    from t.reports
                ) 
ORDER BY updated DESC 
LIMIT 100

如何删除SQL结果中最旧的条目？

4 个答案: