Sql Server 2017
Is it possible to construct a column in SQL that acts as an Identity column for a clustered Primary Key (Value1, Value2, Value3)?
|--------+--------+--------+---------------|
| Value1 | Value2 | Value3 | Identity-ish? |
|--------+--------+--------+---------------|
| 1 | 1 | 1 | 1 |
| 1 | 1 | 1 | 2 |
|--------+--------+--------+---------------|
| 1 | 2 | 1 | 1 |
| 1 | 2 | 1 | 2 |
| 1 | 2 | 1 | 3 |
|--------+--------+--------+---------------|
| 2 | 5 | 3 | 1 |
| 2 | 5 | 3 | 2 |
|--------+--------+--------+---------------|
| 82 | 21 | 13 | 1 |
| 82 | 21 | 13 | 2 |
|--------+--------+--------+---------------|
Currently the way I am tackling this issue is by querying the table for the max(Identity-ish?) on a given PK, and incrementing it when inserting a new record.
However, the scale of the project has reached such a size where this method is getting called too frequently, and sometimes it gets called twice at the same time (causing two identical rows (Value1, Value2, Value3, Identity-ish?))
Ideally I would like to be able to declare Identity-ish? as an Identity column that gets its' values automatically assigned in the way I've shown above.
what you want is I think:
select * from
(
select Value1,Value2,Value3,
row_number ()over (partition by Value1,Value2,Value3 order by
Value1,Value2,Value3) as Identity-ish?
from tablename
)rnk
use ROW_NUMBER()function with partition for column
select t.*,
ROW_NUMBER()
OVER(partition by value1,value2,value3 ORDER BY value1,value2,value3 )
from t
value1 value2 value3 identity_is
1 1 1 1
1 1 1 2
1 2 1 1
1 2 1 2
1 2 1 3
here i put an example
http://www.sqlfiddle.com/#!18/c4b62/4
Related
I'm working on a webapp that tracks tvshows, and I need to get all episodes id's that are season finales, which means, the highest episode number from all seasons, for all tvshows.
This is a simplified version of my "episodes" table.
id tvshow_id season epnum
---|-----------|--------|-------
1 | 1 | 1 | 1
2 | 1 | 1 | 2
3 | 1 | 1 | 3
4 | 1 | 2 | 1
5 | 1 | 2 | 2
6 | 2 | 1 | 1
7 | 2 | 1 | 2
8 | 2 | 1 | 3
9 | 2 | 1 | 4
10 | 2 | 2 | 1
11 | 2 | 2 | 2
The expect output:
id
---|
3 |
5 |
9 |
11 |
I've managed to get this working for the latest season but I can't make it work for all seasons.
I've also tried to take some ideas from this but I can't seem to find a way to add the tvshow_id in there.
I'm using Postgres v10
SELECT Id from
(Select *, Row_number() over (partition by tvshow_id,season order by epnum desc) as ranking from tbl)c
Where ranking=1
You can use the below SQL to get your result, using GROUP BY with sub-subquery as:
select id from tab_x
where (tvshow_id,season,epnum) in (
select tvshow_id,season,max(epnum)
from tab_x
group by tvshow_id,season)
Below is the simple query to get desired result. Below query is also good in performance with help of using distinct on() clause
select
distinct on (tvshow_id,season)
id
from your_table
order by tvshow_id,season ,epnum desc
Given a table like this in PostgreSQL:
Messages
message_id | creating_user_id | receiving_user_id | created_utc
-----------+------------------+-------------------+-------------
1 | 1 | 2 | 1424816011
2 | 3 | 2 | 1424816012
3 | 3 | 2 | 1424816013
4 | 1 | 3 | 1424816014
5 | 1 | 3 | 1424816015
6 | 2 | 1 | 1424816016
7 | 2 | 1 | 1424816017
8 | 1 | 2 | 1424816018
I want to get the newest two rows per creating_user_id/receiving_user_id where the other user_id is 1. So the result of the query should look like:
message_id | creating_user_id | receiving_user_id | created_utc
-----------+------------------+-------------------+-------------
1 | 1 | 2 | 1424816011
4 | 1 | 3 | 1424816014
5 | 1 | 3 | 1424816015
6 | 2 | 1 | 1424816016
Using a window function with row_number() I can get the first 2 messages for each creating_user_id or the first 2 messages for each receiving_user_id, but I'm not sure how to get the first two messages for per creating_user_id/receiving_user_id.
Since you filter rows where one of both columns is 1 (and irrelevant), and 1 happens to be the smallest number of all, you can simply use GREATEST(creating_user_id, receiving_user_id) to distill the relevant number to PARTITION BY. (Else you could employ CASE.)
The rest is standard procedure: calculate a row number in a subquery and select the first two in the outer query:
SELECT message_id, creating_user_id, receiving_user_id, created_utc
FROM (
SELECT *
, row_number() OVER (PARTITION BY GREATEST (creating_user_id
, receiving_user_id)
ORDER BY created_utc) AS rn
FROM messages
WHERE 1 IN (creating_user_id, receiving_user_id)
) sub
WHERE rn < 3
ORDER BY created_utc;
Exactly your result.
SQL Fiddle.
Assume I have this schema (tested on postgresql) where the 'Scorelines' relation contains results of sport matches. (kickoff is a TIMESTAMP but replaced by INT for readability)
SQLFiddle here: http://sqlfiddle.com/#!12/52475/3
CREATE TABLE Scorelines (
team TEXT,
kickoff INT,
scored INT,
conceded INT
);
Now I want to produce another column 'three_matches_scored' that contains the sum of the points scored
over the 3 preceding game (determined by kickoff) of the same team. I have this:
SELECT team, kickoff, scored, conceded, SUM(scored) OVER three_matches AS three_matches_scored
FROM Scorelines
WINDOW three_matches AS
(PARTITION BY team ORDER BY kickoff
ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING)
ORDER BY kickoff;
This works beautifully so far, except that I get values starting from the second game. Example:
| TEAM | KICKOFF | SCORED | CONCEDED | THREE_MATCHES_SCORED |
|------|---------|--------|----------|----------------------|
| A | 1 | 1 | 0 | (null) |
| B | 2 | 1 | 1 | (null) |
| A | 3 | 1 | 1 | 1 |
| A | 4 | 3 | 0 | 2 |
| B | 4 | 1 | 4 | 1 |
| A | 6 | 0 | 2 | 5 |
| B | 6 | 4 | 2 | 2 |
| B | 8 | 1 | 2 | 6 |
| B | 10 | 1 | 1 | 6 |
| A | 11 | 2 | 1 | 4 |
I want the column 'three_matches_scored' to be (null) for the first 3 games because there are no 3 results to sum up. How can I achieve this?
I'd prefer simple understandable solutions, performance is not critical for this particular case.
My only idea right now, is to define a stored function SUM3, that results in (null) with less than 3 values to add up. But I never defined a function in SQL and can't seem to figure it out.
You can use a case statement to null the rows where there are less than 3 games:
SELECT team, kickoff, scored, conceded,
CASE WHEN COUNT(scored) OVER three_matches = 3
THEN SUM(scored) OVER three_matches
ELSE NULL
END AS three_matches_scored
FROM Scorelines
WINDOW three_matches AS
(PARTITION BY team ORDER BY kickoff
ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING)
ORDER BY kickoff;
Output:
team | kickoff | scored | conceded | three_matches_scored
------+---------+--------+----------+----------------------
A | 1 | 1 | 0 |
B | 2 | 1 | 1 |
A | 3 | 1 | 1 |
A | 4 | 3 | 0 |
B | 4 | 1 | 4 |
A | 6 | 0 | 2 | 5
B | 6 | 4 | 2 |
B | 8 | 1 | 2 | 6
B | 10 | 1 | 1 | 6
A | 11 | 2 | 1 | 4
(10 rows)
See harmics answer above.
(my first solution, just for reference)
Solution with user defined aggregate:
CREATE TYPE intermediate_sum AS (
sum INT,
count INT
);
CREATE FUNCTION sum_sfunc(intermediate_sum, INTEGER) RETURNS intermediate_sum AS
$$ SELECT $2 + $1.sum AS sum, $1.count - 1 AS count $$ LANGUAGE SQL;
CREATE FUNCTION sum_ffunc(intermediate_sum) RETURNS INTEGER AS
$$ SELECT (CASE WHEN $1.count > 1 THEN null
WHEN $1.count = 0 THEN $1.sum
END)
$$ LANGUAGE SQL;
CREATE AGGREGATE sum3(INTEGER) (
sfunc = sum_sfunc,
finalfunc = sum_ffunc,
stype = intermediate_sum,
initcond = '(0,3)'
);
The aggregate SUM3 wants at least 3 values, otherwise it returns (null). One can define other aggreates like SUM4 by changing the initcond, for example to '(0,4)'.
My objective is to make dynamic group of lines (of product by TYPE & COLOR in fact)
I don't know if it's possible just with one select query.
But : I want to create group of lines (A PRODUCT is a TYPE and a COLOR) as per the number_per_group column and I want to do this grouping depending on the date order (Order By DATE)
A single product with a NB_PER_GROUP number 2 is exclude from the final result.
Table :
-----------------------------------------------
NUM | TYPE | COLOR | NB_PER_GROUP | DATE
-----------------------------------------------
0 | 1 | 1 | 2 | ...
1 | 1 | 1 | 2 |
2 | 1 | 2 | 2 |
3 | 1 | 2 | 2 |
4 | 1 | 1 | 2 |
5 | 1 | 1 | 2 |
6 | 4 | 1 | 3 |
7 | 1 | 1 | 2 |
8 | 4 | 1 | 3 |
9 | 4 | 1 | 3 |
10 | 5 | 1 | 2 |
Results :
------------------------
GROUP_NUMBER | NUM |
------------------------
0 | 0 |
0 | 1 |
~~~~~~~~~~~~~~~~~~~~~~~~
1 | 2 |
1 | 3 |
~~~~~~~~~~~~~~~~~~~~~~~~
2 | 4 |
2 | 5 |
~~~~~~~~~~~~~~~~~~~~~~~~
3 | 6 |
3 | 8 |
3 | 9 |
If you have another way to solve this problem, I will accept it.
What about something like this?
select max(gn.group_number) group_number, ip.num
from products ip
join (
select date, type, color, row_number() over (order by date) - 1 group_number
from (
select op.num, op.type, op.color, op.nb_per_group, op.date, (row_number() over (partition by op.type, op.color order by op.date) - 1) % nb_per_group group_order
from products op
) sq
where sq.group_order = 0
) gn
on ip.type = gn.type
and ip.color = gn.color
and ip.date >= gn.date
group by ip.num
order by group_number, ip.num
This may only work if your nb_per_group values are the same for each combination of type and color. It may also require unique dates, but that could probably be worked around if required.
The innermost subquery partitions the rows by type and color, orders them by date, then calculates the row numbers modulo nb_per_group; this forms a 0-based count for the group that resets to 0 each time nb_per_group is exceeded.
The next-level subquery finds all of the 0 values we mapped in the lower subquery and assigns group numbers to them.
Finally, the outermost query ties each row in the products table to a group number, calculated as the highest group number that split off before this product's date.
The question isn't very clear, but I'll illustrate what I mean, suppose my table is like such:
item_name | date added | val1 | val2
------------------------------------
1 | date+1 | 10 | 20
1 | date | 12 | 21
2 | date+1 | 5 | 6
3 | date+3 | 3 | 1
3 | date+2 | 5 | 2
3 | date | 3 | 1
And I want to select row 1, 3, 4 as they are the most recent entries for each item
Try this:
select *
from tableX t1
where t1.date_added = (select max(t2.date_added)
from tableX t2
where t2.item_name = t1.item_name )