如何返回最近的值？

Question

timestamp	id	type
2021-06-01T00:00:00	ID1	LOL
2021-06-01T00:00:01	ID2	DOTA
2021-06-01T00:00:02	ID2	DOTA
2020-06-02T00:00:00	ID5	COD
2020-06-02T00:00:01	ID7	VALO
2020-06-02T00:00:02	ID8	VALO
2020-06-02T00:00:03	ID3	DOTA
2020-06-03T00:00:00	ID1	DOTA
2020-06-03T00:00:01	ID1	DOTA
2020-06-03T00:00:02	ID2	DOTA
2020-06-03T00:00:03	ID3	DOTA
2020-06-03T00:00:04	ID4	LOL

I am trying to get a result for all DISTINCT IDS with the most recent type.

Using this query

SELECT DISTINCT id, type
FROM table1
ORDER BY 1; 

I got this result:

id	type
ID1	DOTA
ID1	LOL
ID2	DOTA
ID3	DOTA
ID4	LOL
ID5	COD
ID7	VALO
ID8	VALO

I understand that the row 1 and row 2 have distinct values. I tried querying this to check if it will only return a value with the most recent date. It didn't.

SELECT DISTINCT id, type, MAX(timestamp) date
FROM table1
GROUP BY 1, 2
ORDER BY 1;

id	type	date
ID1	DOTA	2020-06-03 00:00:01
ID1	LOL	2021-06-01 00:00:00
ID2	DOTA	2021-06-01 00:00:02
ID3	DOTA	2020-06-03 00:00:03
ID4	LOL	2020-06-03 00:00:04
ID5	COD	2020-06-02 00:00:00
ID7	VALO	2020-06-02 00:00:01
ID8	VALO	2020-06-02 00:00:02

Tried below query just to check. Returned the same.

SELECT DISTINCT id, type, (SELECT MAX(timestamp) FROM table1 as b where b.timestamp = a.timestamp ) 
FROM table1 as a
GROUP BY 1, 2
ORDER BY 1;

Is my intended result possible?

Answer 1

A simple method uses qualify :

SELECT a.*
FROM chinook.new_table as a
WHERE true
QUALIFY ROW_NUMBER() OVER (PARTITION BY id, type ORDER BY date DESC) = 1;

You can also express this easily using GROUP BY :

SELECT ARRAY_AGG(a ORDER BY date DESC LIMIT 1).*
FROM chinook.new_table a
GROUP BY id, type;

Answer 2

Consider below options

select as value array_agg(t order by timestamp desc limit 1)[offset(0)]
from `project.dataset.table1` t
group by id

or

select *
from `project.dataset.table1` t
where true 
qualify row_number() over(partition by id order by timestamp desc) = 1

both with below output

Answer 3

This provides you groups:

SELECT DISTINCT id, type, MAX(timestamp) date
FROM chinook.new_table as a
GROUP BY 1, 2
ORDER BY 1;

However, seemingly you want a single group for each id , so you will need to somehow aggregate type as well:

SELECT DISTINCT id, GROUP_CONCAT(`type`), MAX(timestamp) date
FROM chinook.new_table as a
GROUP BY 1
ORDER BY 1;

The above will group types into comma-separated values.

Answer 4

Just use GROUP BY

SELECT id, type, MAX(date) AS date_max FROM table1 GROUP BY id,type ORDER BY id,type;