Please help me make a request. i'm at a dead end.
There are 2 tables:
“Trains”:
+----+---------+
| id | numbers |
+----+---------+
| 1 | 101 |
| 2 | 102 |
| 3 | 103 |
| 4 | 104 |
| 5 | 105 |
+----+---------+
“Passages”:
+----+--------------+-------+---------------------+
| id | train_number | speed | date_time |
+----+--------------+-------+---------------------+
| 1 | 101 | 26 | 2021-11-10 16:26:30 |
| 2 | 101 | 28 | 2021-11-12 16:26:30 |
| 3 | 102 | 24 | 2021-11-14 16:26:30 |
| 4 | 103 | 27 | 2021-11-15 16:26:30 |
| 5 | 101 | 29 | 2021-11-16 16:26:30 |
+----+--------------+-------+---------------------+
The goal is to go through the train numbers from the Trains table, take from the existing ones from the Passages table by the latest date (date_time) and the number of passages for “the last date for each train” - N days. as I understand date_time - interval "N days". should get something like:
+----+--------+---------------------+----------------+
| id | train | last_passage | count_passages |
+----+--------+---------------------+----------------+
| 1 | 101 | 2021-11-10 16:26:30 | 2 |
| 2 | 102 | 2021-11-14 16:26:30 | 1 |
| 3 | 103 | 2021-11-15 16:26:30 | 1 |
| 4 | 104 | null | 0 |
| 5 | 105 | null | 0 |
+----+--------+---------------------+----------------+
ps: "count_passages" - for example, last passage date minus 4 days
I tried through "where in" but I can’t create the necessary and correct request
select * from rankings;
students | stu_id | card_id
----------+--------+---------
Charlie | 11 | 1
Shakira | 22 | 2
Selena | 33 | 3
Ross | 44 | 4
Chandler | 55 | 5
James | 66 | 6
Kylie | 77 | 7
Here is the table kindly tell me how we can apply the rank function in it with Postgresql?
This question already has answers here:
Select first row in each GROUP BY group?
(20 answers)
Closed 3 years ago.
At the moment I'm struggling with a problem that looks very easy.
Tablecontent:
Primay Keys: Timestamp, COL_A,COL_B ,COL_C,COL_D
+------------------+-------+-------+-------+-------+--------+--------+
| Timestamp | COL_A | COL_B | COL_C | COL_D | Data_A | Data_B |
+------------------+-------+-------+-------+-------+--------+--------+
| 31.07.2019 15:12 | - | - | - | - | 1 | 2 |
| 31.07.2019 15:32 | 1 | 1 | 100 | 1 | 5000 | 20 |
| 10.08.2019 09:33 | - | - | - | - | 1000 | 7 |
| 31.07.2019 15:38 | 1 | 1 | 100 | 1 | 33 | 5 |
| 06.08.2019 08:53 | - | - | - | - | 0 | 7 |
| 06.08.2019 09:08 | - | - | - | - | 0 | 7 |
| 06.08.2019 16:06 | 3 | 3 | 3 | 3 | 0 | 23 |
| 07.08.2019 10:43 | - | - | - | - | 0 | 42 |
| 07.08.2019 13:10 | - | - | - | - | 0 | 24 |
| 08.08.2019 07:19 | 11 | 111 | 111 | 12 | 0 | 2 |
| 08.08.2019 10:54 | 2334 | 65464 | 565 | 76 | 1000 | 19 |
| 08.08.2019 11:15 | 232 | 343 | 343 | 43 | 0 | 2 |
| 08.08.2019 11:30 | 2323 | rtttt | 3434 | 34 | 0 | 2 |
| 10.08.2019 14:47 | - | - | - | - | 123 | 23 |
+------------------+-------+-------+-------+-------+--------+--------+
Needed query output:
+------------------+-------+-------+-------+-------+--------+--------+
| Timestamp | COL_A | COL_B | COL_C | COL_D | Data_A | Data_B |
+------------------+-------+-------+-------+-------+--------+--------+
| 31.07.2019 15:38 | 1 | 1 | 100 | 1 | 33 | 5 |
| 06.08.2019 16:06 | 3 | 3 | 3 | 3 | 0 | 23 |
| 08.08.2019 07:19 | 11 | 111 | 111 | 12 | 0 | 2 |
| 08.08.2019 10:54 | 2334 | 65464 | 565 | 76 | 1000 | 19 |
| 08.08.2019 11:15 | 232 | 343 | 343 | 43 | 0 | 2 |
| 08.08.2019 11:30 | 2323 | rtttt | 3434 | 34 | 0 | 2 |
| 10.08.2019 14:47 | - | - | - | - | 123 | 23 |
+------------------+-------+-------+-------+-------+--------+--------+
As you can see, I'm trying to get single rows for my primary keys, using the latest timestamp, which is also a primary key.
Currently, I tried a query like:
SELECT Timestamp, COL_A, COL_B, COL_C, COL_D, Data_A, Data_B From Table XY op
WHERE Timestamp = (
SELECT MAX(Timestamp) FROM XY as tsRow
WHERE op.COL_A = tsRow.COL_A
AND op.COL_B = tsRow.COL_B
AND op.COL_C = tsRow.COL_C
AND op.COL_D = tsRow."COL_D
);
which gives me result that looks fine at first glance.
Is there a better or more safe way to get my preferred result?
demo:db<>fiddle
You can use the DISTINCT ON clause, which gives you the first record of an ordered group. Here your group is your (A, B, C, D). This is ordered by the Timestamp column, in descending order, to get the most recent record to be the first.
SELECT DISTINCT ON ("COL_A", "COL_B", "COL_C", "COL_D")
*
FROM
mytable
ORDER BY "COL_A", "COL_B", "COL_C", "COL_D", "Timestamp" DESC
If you want to get your expected order, you need a second ORDER BY after this operation:
SELECT
*
FROM (
SELECT DISTINCT ON ("COL_A", "COL_B", "COL_C", "COL_D")
*
FROM
mytable
ORDER BY "COL_A", "COL_B", "COL_C", "COL_D", "Timestamp" DESC
) s
ORDER BY "Timestamp"
Note: If you have the Timestamp column as part of the PK, are you sure, you really need the four other columns as PK as well? It seems, that the TS column is already unique.
I'm trying to compare different costs from different periods. But I dont no how I can compare the single record with the record before and after. What I need is a yes or no in my dataset when the costs from a records is the same as record before and record after.
My dataset looks like this:
+--------+-----------+----------+------------+-------+-----------+
| Client | Provision | CAK Year | CAK Period | Costs | Serial Nr |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2017 | 13 | 150 | 1 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2018 | 1 | 200 | 2 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2018 | 2 | 170 | 3 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2018 | 3 | 150 | 4 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2018 | 4 | 150 | 5 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 210 | 2018 | 5 | 150 | 6 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 689 | 2018 | 1 | 345 | 1 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 689 | 2018 | 2 | 345 | 1 |
+--------+-----------+----------+------------+-------+-----------+
| 1 | 689 | 2018 | 3 | 345 | 1 |
+--------+-----------+----------+------------+-------+-----------+
What i've tried so far:
CASE
WHEN Provision = Provision
AND Costs = LEAD(Costs, 1, 0) OVER(ORDER BY CAK Year, CAK Period)
AND Costs = LAG(Costs, 1, 0) OVER(ORDER BY CAK Year, CAK Period)
THEN 'Yes
ELSE 'No'
END
My expected result:
+--------+-----------+----------+------------+-------+-----------+--------+
| Client | Provision | CAK Year | CAK Period | Costs | Serial Nr | Result |
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2017 | 13 | 150 | 1 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2018 | 1 | 200 | 2 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2018 | 2 | 170 | 3 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2018 | 3 | 150 | 4 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2018 | 4 | 150 | 5 | Yes
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 210 | 2018 | 5 | 150 | 6 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 689 | 2018 | 1 | 345 | 1 | No
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 689 | 2018 | 2 | 345 | 1 | Yes
+--------+-----------+----------+------------+-------+-----------+--------+
| 1 | 689 | 2018 | 3 | 345 | 1 | No
+--------+-----------+----------+------------+-------+-----------+--------+
You guys can help me further because I don't get the expected result?
You need to add in partition by Provision otherwise your lag and lead ordering will run across all Provision values:
declare #d table(Client int,Provision int,CAKYear int, CAKPeriod int, Costs int, SerialNr int);
insert into #d values
(1,210,2017,13,150,1)
,(1,210,2018,1,200,2)
,(1,210,2018,2,170,3)
,(1,210,2018,3,150,4)
,(1,210,2018,4,150,5)
,(1,210,2018,5,150,6)
,(1,689,2018,1,345,1)
,(1,689,2018,2,345,1)
,(1,689,2018,3,345,1);
select *
,case when Provision = Provision
and Costs = lead(Costs, 1, 0) over(partition by Provision order by CAKYear, CAKPeriod)
and Costs = lag(Costs, 1, 0) over(partition by Provision order by CAKYear, CAKPeriod)
then 'Yes'
else 'No'
end as Result
from #d
order by Provision
,CAKYear
,CAKPeriod;
Output
+--------+-----------+---------+-----------+-------+----------+--------+
| Client | Provision | CAKYear | CAKPeriod | Costs | SerialNr | Result |
+--------+-----------+---------+-----------+-------+----------+--------+
| 1 | 210 | 2017 | 13 | 150 | 1 | No |
| 1 | 210 | 2018 | 1 | 200 | 2 | No |
| 1 | 210 | 2018 | 2 | 170 | 3 | No |
| 1 | 210 | 2018 | 3 | 150 | 4 | No |
| 1 | 210 | 2018 | 4 | 150 | 5 | Yes |
| 1 | 210 | 2018 | 5 | 150 | 6 | No |
| 1 | 689 | 2018 | 1 | 345 | 1 | No |
| 1 | 689 | 2018 | 2 | 345 | 1 | Yes |
| 1 | 689 | 2018 | 3 | 345 | 1 | No |
+--------+-----------+---------+-----------+-------+----------+--------+
My table is:
id sub_id datetime resource
---|-----|------------|-------
1 | 10 | 04/03/2009 | 399
2 | 11 | 04/03/2009 | 244
3 | 10 | 04/03/2009 | 555
4 | 10 | 03/03/2009 | 300
5 | 11 | 03/03/2009 | 200
6 | 11 | 03/03/2009 | 500
7 | 11 | 24/12/2008 | 600
8 | 13 | 01/01/2009 | 750
9 | 10 | 01/01/2009 | 760
10 | 13 | 01/01/2009 | 570
11 | 11 | 01/01/2009 | 870
12 | 13 | 01/01/2009 | 670
13 | 13 | 01/01/2009 | 703
14 | 13 | 01/01/2009 | 705
I need to select for each sub_id only 2 times
Result would be:
id sub_id datetime resource
---|-----|------------|-------
1 | 10 | 04/03/2009 | 399
3 | 10 | 04/03/2009 | 555
5 | 11 | 03/03/2009 | 200
6 | 11 | 03/03/2009 | 500
8 | 13 | 01/01/2009 | 750
10 | 13 | 01/01/2009 | 570
How can I achieve this result in postgres ?
Use the window function row_number():
select id, sub_id, datetime, resource
from (
select *, row_number() over (partition by sub_id order by id)
from my_table
) s
where row_number < 3;
look at the order column (I use id to match your sample):
t=# with data as (select *,count(1) over (partition by sub_id order by id) from t)
select id,sub_id,datetime,resource from data where count <3;
id | sub_id | datetime | resource
----+--------+------------+----------
1 | 10 | 2009-03-04 | 399
3 | 10 | 2009-03-04 | 555
2 | 11 | 2009-03-04 | 244
5 | 11 | 2009-03-03 | 200
8 | 13 | 2009-01-01 | 750
10 | 13 | 2009-01-01 | 570
(6 rows)