Mysql select last row for each group

问题

SELECT  
MAX('time'), c_id, message, state, time 
FROM message 
WHERE receive = 1 
GROUP BY c_id

I have a mysql query, I try to select the last row of each group, but it's not working.

c_id is the group. It select the first row of each group now.

回答1:

First, you should not escape the column name with single quote since it is not string literal.
Second, you can do subquery which separately get the latest time for every c_id and join it back with the original table to get the other columns.

SELECT  a.*
FROM    message a
        INNER JOIN
        (
            SELECT  c_id, MAX(time) time
            FROM    message
            GROUP   BY c_id
        ) b ON a.c_id = b.c_id AND
                a.time = b.time

or

SELECT  a.*
FROM    message a
WHERE   a.time =
        (
            SELECT  MAX(time) time
            FROM    message b
            WHERE   a.c_id = b.c_id
        ) 

回答2:

Thanx to John Woo!

SELECT a.* FROM survey_question_option a INNER JOIN (
   SELECT    subordinate_question, MAX(sort) sort
   FROM      survey_question_option 
   WHERE     question_id=14
   GROUP BY  subordinate_question
) b ON ((a.subordinate_question = b.subordinate_question) OR (a.subordinate_question IS NULL AND b.subordinate_question IS NULL)) AND
a.sort = b.sort AND a.question_id=14;

来源：https://stackoverflow.com/questions/17830355/mysql-select-last-row-for-each-group