Mysql 复杂的SQL联接查询-获取最新行

mymysqldb有一个表（cfg），其中有4个字段：id、name、data和location 这一个表用于服务多个子域（位置）。我需要为给定子域（位置）的每个名称获取最新行的列表

示例数据

id   name   data   location
---------------------------
1    color  red    dc
2    color  blue   dc
3    size   large  sj
4    color  green  sj
5    size   small  dc

下面的查询工作正常，但似乎太复杂和缓慢。有人有什么建议吗

SELECT c1.name, c1.data
FROM (SELECT * FROM cfg WHERE location = "dc") as c1
LEFT JOIN (SELECT * FROM cfg WHERE location = "dc") as c2 ON ( c1.name = c2.name
AND c1.id < c2.id )
WHERE c2.id IS NULL

---

使用带有

分组依据的子查询，计算每个
名称的最大
id
：

SELECT cfg.*
FROM   cfg
JOIN  (
    SELECT max(id) AS max_id
    FROM   cfg c0
    WHERE  location = 'dc'
    GROUP  BY name
    ) n ON n.max_id = cfg.id

我想

select c.name, c.data
from cfg c
join (
 select max(id) id
 from cfg
 group by name
 where location = 'dc'
) nameMaximums on nameMaximums.id = c.id 

并在（位置、名称、id）上使用索引，在（id）上使用索引

这只是未经测试的徒手，但我想你明白了。这假定列id是唯一的

select c.name, c.data
from cfg c
join (
 select max(id) id
 from cfg
 group by name
 where location = 'dc'
) nameMaximums on nameMaximums.id = c.id 

select name, data
from cfg
where id in (select max(id) from cfg where location = "dc" group by name)