如何使用SQl语法从MySQL表中的组中选择最新记录

Question

I'm trying to get the latest row of each group.

$SQL = "SELECT location_name, status, timecode FROM status_table WHERE location_name in ('G_01', 'J_01', 'M_01', 'A_01', 'U_01', 'W_01', 'W_1_01', 'C_01', 'G_2_01', 'M_01') GROUP BY location_name ORDER BY status";

The query only pull up the first row, and order by timecode does not work

Answer 1

It will only pull the first row because the group by is only on one column.

Try including your other selected fields in the GROUP BY clause

$SQL = "SELECT location_name, status, timecode FROM status_table 
WHERE location_name in  
('G_01', 'J_01', 'M_01', 'A_01', 'U_01', 'W_01', 'W_1_01', 'C_01', 'G_2_01', 'M_01') 
GROUP BY location_name, status, timecode 
ORDER BY status";

Answer 2

If you have an auto incrementing id column:

SELECT location_name, status, timecode FROM status_table WHERE id IN(
   SELECT MAX(id) FROM status_table WHERE location_name in ('G_01', 'J_01', 'M_01', 'A_01', 'U_01', 'W_01', 'W_1_01', 'C_01', 'G_2_01', 'M_01') GROUP BY location_name
) ORDER BY status

Should work by getting the MAX id for each "group" (location name) then get the details for that id, and finally order the resultset by status

Answer 3

I cant get you properly but till i understand i think below links really help you

1) php/MySQL insert row then get 'id'
2) Get the id of current mysql insert
3) MySQL - Select the last inserted row easiest way
4) mysql_insert_id

i hope above links are helpful....