如何在mysql中获取每天的最后一条记录？

Question

I want to get last record of each day in mysql. Location<id, date, place_id> table has multiple entries on each day. This Location table has place_id and time at which place_id is inserted.

Also taking consider if place_id is not present then return second last record which has place_id. In following table for NULL, '2016-04-06 18:52:06' record we are returning '13664', '2016-04-06 12:57:30' , which is second last record on '2016-04-06' (6th March) and has place_id.

One more thing, on single day, there would be more place_id, see the following table..

   id  ||  place_id || date
   '1',   '47', '2016-04-05 18:09:37'
   '2',   '48', '2016-04-05 12:09:37'
   '3',   '13664', '2016-04-06 12:57:30'
   '4',   '9553', '2016-04-08 10:09:37'
   '5',   NULL, '2016-04-06 18:52:06'
   '6',   '9537', '2016-04-07 03:34:24'
   '7',   '9537', '2016-04-07 03:34:24'
   '8',   '656', '2016-04-07 05:34:24'
   '9',   '7', '2016-04-07 05:34:57'

When I run following query it returns following result

Query I run the following query but it is giving me wrong result

`Location<id, place_id, date>`

select L1.place_id, L1.date from 
     Location1 L1 
Left join
     Location1 L2
on 
     Date(L1.date) = Date(L2.date)
And
    L1.date < L2.date
where 
    L2.date is null

group by L1.date;

Result I want:

 id....place_id ........date   
   '1',   '47',      '2016-04-05 18:09:37'    
   '3',   '13664',   '2016-04-06 12:57:30'  
   '4',   '9553',    '2016-04-08 10:09:37'   
   '9',   '7',       '2016-04-07 05:34:57'

Answer 1

You may give it a try:

SELECT 
L.id,
L.place_id,
L.date
FROM Location L
INNER JOIN 
(
  SELECT 
   MAX(date) max_time
  FROM Location
  GROUP BY Date(`date`)
) AS t
ON L.date = t.max_time

SQL FIDDLE DEMO

SQL FIDDLE DEMO2

[ Based on your expected output ]

Answer 2

Can you try with the following query:

SELECT * FROM `Location` GROUP BY DATE(`date`) ORDER BY `date` DESC

What this query does is group the rows by descending date and show a row for each date.

Get the last record:

SELECT * FROM `Location` ORDER BY `date` LIMIT 1;

Get the last record that doesn't have a null as a value:

SELECT * FROM `Location` WHERE place_id IS NOT NULL ORDER BY `date` LIMIT 1;

Get records for all the places which are not null:

SELECT * FROM `Location` WHERE place_id IS NOT NULL GROUP BY `place_id` ORDER BY `date` DESC

Answer 3

Would this work?

select place_id, max(date) as MaxDate
from foo
where place_id is not NULL
group by place_id