mysql - MySQL：具有最少日期的唯一行

Question

想象一下我有下表：

NAME DATE OTHER_CONTANT

'A' '2012-06-05' 'baz'
'A' '2012-06-04' 'bar'
'B' '2012-06-05' 'foo'
'C' '2012-06-05' 'bla'
'C' '2012-06-04' 'blah'
'C' '2012-06-06' 'bleh'

现在我想过滤此表以仅包含具有唯一名称和最早日期的行：

'A' '2012-06-04' 'bar'
'B' '2012-06-05' 'foo'
'C' '2012-06-04' 'blah'

我正在考虑使用 GROUP BY 语句，但是使用 GROUP BY 我只能得到一列作为结果，我想得到整行。有关如何进行此过滤的任何建议？

Answer 1

您可以使用以下内容：

select m.name, m.date, m.other_constant 
  from mytable m
  join (select name, min(date) min_date from mytable group by name) n
    on m.name = n.name and m.date = n.min_date

另请参阅SQLfiddle。

Answer 2

以下 SQL 创建所有不同名称的列表。然后对于每个名称，它会查找具有最新日期的条目。

select  *
from    (
        select  distinct name
        from    YourTable
        ) names
join    YourTable yt1
on      yt1.name = names.name
        and yt1.date =
        (
        select  date
        from    YourTable yt2
        where   yt2.name = yt1.name
        order by
                date
        limit   1
        )

使用 beny23 的 SQL Fiddle 的实时示例。

Answer 3

两个查询都可以完美运行。

SELECT * 
FROM   MyTable a 
       INNER JOIN (SELECT name, 
                          Min(date) AS date 
                   FROM   MyTable 
                   GROUP  BY name) b 
               ON a.name = b.name 
                  AND a.date = b.date

或者

SELECT a.* 
FROM   mytable a 
       LEFT JOIN mytable b 
              ON a.name = b.name
                 AND a.date > b.date 
WHERE  b.name IS NULL 

Answer 4

select *
from (
   select name, min(date) as mindate, other_contact
   from table_name group by name
   ) as x
   inner join table_name as f 
   on f.name = x.name and f.date= x.mindate; 

Answer 5

SELECT
    a.name,
    a.date,
    b.other_contant
FROM
    (
        SELECT
            name,
            MIN(date) AS date,
        FROM
            yourtable
        GROUP BY 
            name
    ) a
INNER JOIN
    yourtable b ON a.name = b.name AND a.date = b.date