Questions tagged [recursive]
Using recursion to solve database problems.
27 questions
6
votes
2
answers
4k
views
Improve performance for order by with columns from many tables
Using PostgreSQL 8.4, I'm trying to consult two tables with 1 million records using order by with indexed columns of the two tables, and I'm losing performance (with 1 column takes 30 ms and with two ...
2
votes
1
answer
14k
views
Recursive Query in MySQL using stored proceedure and CURSOR
I'm expanding our user/group system to allow for dynamic groups which are made up of other groups members. I have three tables users, groups, and relationships.
For simplicity sake, lets say users ...
- 506
33
votes
2
answers
12k
views
Using EXCEPT in a recursive common table expression
Why does the following query return infinite rows? I would have expected the EXCEPT clause to terminate the recursion..
with cte as (
select *
from (
values(1),(2),(3),(4),(5)
) ...
- 2,179
5
votes
1
answer
2k
views
How to turn a set of flat trees into a single tree with multiple leaves?
We have this beautiful Postgres tree generator. Yet it kind of produces cuts of a tree not a whole tree all at once:
item_id jsonb_pretty
1 {
"title": "PARENT",
"...
- 75
1
vote
1
answer
510
views
Recursive Parent-Child Location Relationship Cache as View
Here is my data structure:
CREATE TABLE Locations(
LocID int IDENTITY(1,1) NOT NULL,
LocationTypeID int NOT NULL,
ParentID int NULL,
LocNum varchar(50) NULL,
LocName varchar(250) ...
- 127
20
votes
5
answers
9k
views
How to recursively find gaps where 90 days passed, between rows
This is a kind of trivial task in my C# homeworld, but I don't yet make it in SQL and would prefer to solve it set-based (without cursors). A resultset should come from a query like this.
SELECT ...
- 213
19
votes
1
answer
14k
views
How do I sort the results of a recursive query in an expanded tree-like fashion?
Let's assume you have a nodes tables like this:
CREATE TABLE nodes (
node serial PRIMARY KEY,
parent integer NULL REFERENCES nodes(node),
ts timestamp NOT NULL DEFAULT now()
);
It ...
- 525
17
votes
2
answers
15k
views
Recursive CTE to find Total for all children
Here is an assembly tree that I want to search using a recursive T-SQL Query (presumably CTE) with the expected results below. I want to know the total amount per assembly given any part.
Meaning if ...
- 314
14
votes
4
answers
73k
views
Getting all descendants of a parent
I have a table with two columns, Parent and Child.
I need to get the list of all descendants associated with the parent records.
Source Table
+----+-----------+
| Parent | Child |
+----+-----------+
...
- 261
10
votes
1
answer
3k
views
Simplifying Function with Recursive CTE and/or Window Function
I'm trying to come up with a Recursive CTE and/or Window Function to create a function.
After days, I've boiled the function down to (pseudocode)
where I have N and B, and need to generate E:
En =...
- 232
10
votes
2
answers
3k
views
self-joins in recursive CTE: `recursive reference must not appear more than once`?
This is tested with PostgreSQL 9.6, but it's a general SQL question.
Is it possible to use self-joins of the recursive table in a recursive CTE (rCTE)?
I tried the following rCTE containing a self-...
- 3,692
9
votes
2
answers
7k
views
PostgreSQL - retrieve all IDs in a tree for a given subnode
I have a non-binary tree of customer, and I need to obtain all the IDs in a tree for the given node.
The table is very simple, just an join table with a parent id and child id.
This is a ...
- 123
7
votes
1
answer
4k
views
Recursive CTE based on function values significantly slower on Postgres 12 than on 11
Following up on my question about some queries in Postgres 12 being slower than in 11 I think, I was able to narrow down the problem. It seems like one recursive CTE based on function values is the ...
- 479
7
votes
1
answer
2k
views
Recursive CTE to find unique slug
I have an article table where I want the slug to be unique.
CREATE TABLE article (
title char(50) NOT NULL,
slug char(50) NOT NULL
);
When the user enters a title e.g. News on Apple, I want ...
- 1,119
6
votes
3
answers
1k
views
How can I calculate all grouping permutations of an input string in SQL?
Given an input like "ABC" generate a query that calculates all potential splits of 0 or more of the given string,
Desired output,
A B C
A BC
AB C
ABC
Given an input like "ABCD&...
- 64.6k
5
votes
2
answers
8k
views
Create JSON object from recursive tree structure
Having this simple many-to-many self-referential structure.
An item owns other items through the joins table:
CREATE TABLE items (
item_id serial PRIMARY KEY
, title text
);
CREATE TABLE ...
- 179
4
votes
1
answer
5k
views
Making a recursive CTE like query, but for many records
I have a table with a hierarchy ( with a recursive parentID column), for one record, I know how to get the last parent record, with the following code :
declare @Id integer
;WITH CTE AS
(
SELECT ...
- 43
4
votes
0
answers
984
views
Recursive BOM (Bill Of Material) type query
I have what I've been told is a Bill Of Material type query - which requires a 'recursive' query. I've never heard of such a thing - and was hoping to get some help.
My schema stores asset / asset-...
- 41
4
votes
1
answer
2k
views
Preserve order of array elements after join
I have a query that returns a CTE looking like
+-----------+-------------+
| node_id | ancestors |
|-----------+-------------|
| 1 | [] |
| 2 | [] |
| 3 |...
- 143
3
votes
1
answer
860
views
Get the total count of every child foreign keys
I have been trying this in SQL EXPRESS 2016. Here is my problem:
I have a tree like structure DB(Parent > child > grandchild >...) and in the lower level there is a relation with another table.
...
- 43
3
votes
1
answer
5k
views
Recursively find the path to all leaves descending from a given parent in a tree
I'm trying to write a query to identify the path to each furthest descendant of a particular parent node in a table of tree structures like:
0 1
| |
2 3
| |
4 5
...
- 155
2
votes
0
answers
483
views
Drop intermediate results of recursive query in Postgres
I'm trying to aggregate the contents of a column from a directed acyclic graph (DAG) stored in a Postgres table.
Each dag row has an id, bytes, and may also have a parent referencing another row. I'm ...
- 155
1
vote
1
answer
2k
views
Self-join unique pairs
I have a table (players) containing a list of players, I would like to pair up these players in a unique way, so that every player's opponent is unique every round (ie. every time the SELECT query is ...
- 588
1
vote
1
answer
2k
views
Social network comments and posts model in PostgreSQL 9.6
I'm trying to figure out a data structure for migrating from MongoDB to PostgreSQL. Within my posts table in Postgres, I have a JSONB[] array holding comments for the post.
The thing is that each ...
Duxducis
0
votes
2
answers
4k
views
Postgresql split single row into multiple rows based on date [duplicate]
In my case, we have a table ABC with the supposed 1 row.
id
name
start_date
end_date
1
Rahul
01/01/2021
06/01/2021
but while retrieving I would like to get multiple rows where the start date is ...
- 115
0
votes
0
answers
385
views
How to optimize (or get an alternative faster solution to) this recursive query that groups using recursive CTEs in Postgres?
I am on the quest to implement an NMS filter for labels in a Database.
For context, here's a link to my first question, where I explain what NMS is and what I'm trying to achieve (I will edit that ...
- 51
0
votes
5
answers
4k
views
Finding the first parent (manager) of an employee that makes twice as much in a self-referencing table?
Example you have the following table
CREATE TABLE emp (id,name,salary,manager)
AS
VALUES
( 1 , 'james' , 10000 , null ),
( 2 , 'alex' , 5000 , 1 ),
( 3 , 'Alice' , 4500 , 1 ),
...
