如何根据一列的最大值从MySQL中选择行并分组其他两列?

How can I select rows from MySQL based on max value of a one column and grouping two other columns? The query needs to group by code, group by element_id with where clause (element_id=1.B.1.b) and max(data_value).

如何根据一列的最大值从MySQL中选择行并分组其他两列?查询需要按代码进行分组，使用where子句(element_id= 1.b .1 b)和max(data_value)进行分组。

code        element_id  data_value
11-1011.00  1.B.1.a     1.33        
11-1011.00  1.B.1.b     2.00    
11-1012.00  1.B.1.a     2.67    
11-1012.00  1.B.1.b     3.67    
11-1012.00  1.B.1.C     7.00

I have tried this:

我试过这个:

SELECT * FROM (select
  max(`data_value`) as maxID, `code`, `element_id`
from
  table_name
GROUP BY `code`, `element_id`
ORDER BY maxID desc) abc
GROUP BY `code`

in that table i have lots of data. its a sample.

在那张桌子上我有很多资料。它的一个示例。

Here you can see more clear:

在这里你可以看到更清晰的:

I need result :

我需要结果:

11-1011.00 1.B.1.b 2.00

11 - 1011.00 - 1.责任。b 2.00

11-1012.00 1.B.1.c 7.00

11 - 1012.00 - 1.责任。c 7.00

this result for without where clasuse.

这个结果在哪里都没有。

if using where clause i want only one result that match with element_id(1.B.1.b) that i have:

如果使用where子句，我只想要一个与element_id(1.B.1.b)匹配的结果:

11-1011.00 1.B.1.b 2.00

11 - 1011.00 - 1.责任。b 2.00

2 个解决方案

#1

You can achieve this by

你可以做到这一点。

SELECT a.code, max( a.maxID ) , a.element_id
FROM (
    SELECT *
    FROM (
        SELECT max(data_value) AS maxID, code , element_id
        FROM table_name
        GROUP BY code , element_id
        ORDER BY maxID DESC
    ) AS abc
    GROUP BY code
) AS a
WHERE a.element_id = '1.B.1.b'
GROUP BY a.code
ORDER BY a.code

or try this

或者试试这个

SELECT a.code, a.element_id, a.data_value
FROM interests a
INNER JOIN (
    SELECT code, max( data_value ) data_value
    FROM table_name
    GROUP BY code
)b ON a.code = b.code
AND a.data_value = b.data_value
WHERE a.element_id = '1.B.1.b'
ORDER BY a.code

#2

So, you want to group by code and element_id, and select the max data_value. This can be achieved by.

因此，您希望按代码和element_id进行分组，并选择最大data_value。这可以通过。

SELECT
    code,
    element_id,
    max(data_value) AS data_value
FROM table_name
GROUP BY
    code,
    element_id

Now, if there are a lot more columns within table_name, you'll want to make the previous a query a sub-query, join to table_name, and then select your desired columns.

现在，如果table_name中有更多的列，那么您将希望将前面的查询变成子查询，连接到table_name，然后选择所需的列。

SELECT table_name.*
FROM (
    SELECT
        code,
        element_id,
        max(data_value) AS data_value
    FROM table_name
    GROUP BY
        code,
        element_id
) AS max_record
INNER JOIN table_name
    ON table_name.code = max_record.code
    AND table_name.element_id = max_record.element_id
    AND table_name.data_value = max_record.data_value

#1