Questions tagged [self-join]

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Explaining what the OR operator does in the following code

I ran into the following SQL code which (successfully) outputs a list of parents and the age of their youngest child: SELECT parents.name AS name, MIN(children.age) AS age FROM people children INNER ...
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1answer
24 views

Multiple self joins where joining condition not always exists

I am trying to perform a multiple self join query where one of the conditions it is joining on does not always exist. I have a table that stores different sale events, where a single transaction (...
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1answer
34 views

MariaDB: Why is this still using temporary and filesort - is it because I'm using a self-join? How to fix?

SELECT e2.personId, COUNT(*) FROM entries e1 JOIN entries e2 ON e2.categoryId = e1.categoryId AND e2.personId != e1.personId WHERE e1....
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50 views

T-SQL: how to show the corresponding column's row to an aggregating function's result?

Everyone, I have a question - how to show the (possibly ambiguous) column that corresponds to the value retrieved by an aggregating function? Related to the dataset below, the task is to find the ...
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1answer
17 views

SQLite - Counting referenced rows in one table using a different, related self-referencing table

media_subscriptions +----+--------------------------+ | id | target_metadata_item_id | +----+--------------------------+ | 30 | 19039 | | 31 | NULL | | 32 | ...
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Matching columns within the same table in SQLite

I have a table of Employees which contain, among other things, the employeeId, the lastName and the ReportsTo column, that refers to the manager ID to which the employee has to report. That manager is ...
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2answers
28 views

How to optimize selection of pairs from one column of the table (self-join)?

I'm using PostgreSQL 9.5.19, DBeaver 6.3.4 I have a table where one row is - user's name, place he attended, time when he was there I need to select all pairs of places where any user was (if user ...
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1answer
39 views

Group by unknown ID, select all related rows where Column X = Y and Column X = Z

I have a table that logs interactions from users with the following structure. SELECT [SessionID] ,[Question] ,[Response] ,[DateCreated] ,[Terminal] FROM [Quiz] where Teminal ...
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1answer
111 views

Recursivly get a Tree Via self joined table

Using other questions here & Postgresql documentation I've managed to build a many-to-many self joined table. However adding a WHERE clause is giving me trouble. Problem: A Category can have ...
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1answer
31 views

accelerating a SQL quadruple self-join with a complex alternation in the WHERE clause

The following Sqlite query has a triple self-join on table t: SELECT "update_variable", lhs_acc.name_suffix || ":" || rhs_var.name_suffix, op.span, op.path FROM t op JOIN t lhs_acc ON (...
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1answer
17 views

Join a table to itself, each row needs to join to the ordered last record

I have a logging table which for whatever reason logs the column and table that changed, the date it changed and also the value it was changed FROM (the old value). I want to join these records ...
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1answer
16 views

Selecting Multiple Values from Same Coulmn

I want a query to find out who doesn't have a specific role (user, create or admin) DB is Structured as Follows: name_last | name_first | role Sample Data: brown | john | user | brown | john | ...
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1answer
26 views

How to retrieve data from a table with two of the columns in the table with the same value?

UserName, UserID, FollowingUserID 'RachelLim', '1003', '1004' 'YunaKim', '1005', '1007' 'AustinLee', '1007', '1005' 'BenChoi', '1010', '1001' 'RebeccaFang', '1009', '1004' 'AliceAng', '1004', '1003' ...
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2answers
50 views

Select the students that are enrolled in both the courses [closed]

This is the table definition. I want to select the students that are enrolled in courses (1 and 3). From this dataset the expected output is 'B'.
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1answer
144 views

write SQL query that takes its own output as input

In a table that displays how trades are related to each other, starting from one trade, I want to find all other trades that relate to the first trade: 713613 PostPTETradeIDs 718478 713613 ...
4
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1answer
160 views

Is it possible to upsert into a self-referencing table with a single statement in PostgreSQL?

If I have a table A, like so: A { id SERIAL title TEXT ... parentId INT references A.id via a foreign key constraint } I am pulling data from a source table - A_SOURCE - where there isn't a ...
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38 views

Postgres count the same join by different values

I've been trying to create a query that counts the number of different types of events associated with each entry in another table city job job_events id | name | state ...
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3answers
681 views

Usage of aggregate function with when self-joining a table

I want to find people from a database who has a weight bigger then the average weight: SELECT * FROM Player p1, Player p2 WHERE p1.weight > avg(p2.weight) But I have an error: Result: misuse of ...
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1answer
67 views

Select most recent event for each plate on a property unless the most recent is “Out” - self-join?

My cameras are positioned on the entry and exit gates of a parking garages. As cars pass the cameras, they capture the license plate and other attributes and load it into a database in real time. I ...
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1answer
281 views

Self-join example review in Books Online

Here in this example it states that performs a self-join, but it joins Sales.SalesPerson to Sales.SalesTerritory. I knew that self join means joining the same table to itself but here aren't Sales....
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2answers
172 views

Can a transitive join loop infinitely?

I have a table that stores alternative product: +--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------...
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2answers
388 views

Joining two ltree based tree tables recursively

I have two tables, roles and permissions, both of which use ltree for maintaining a tree structure. I also have a pivot table, roles_permissions, which serves to connect the two tables. How can I join ...
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1answer
3k views

Avoid duplicates on self join

Given the following table my_table : my_column ------ A B C D I would like to be able to join on itself but without duplicate pairs like so: -- SELECT a.*, b.* FROM my_table a JOIN my_table b ON a....
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1answer
800 views

how to make sql statement to find siblings in a table [closed]

I have a question here which need your kindly help. I have a table with the following data family_id,student_Name --------- ------------ A,Tom B,Jack C,Steve B,Terry C,Jerry And then I want to write ...
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1answer
40 views

JOIN by part of two column names

Consider a table with the structure of id col1 WqDs.first WqDs.second eeRT.first eeRT.second How can I JOIN the table to itself using the first part of the id SELECT idxx, a.col1 AS ...
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1answer
2k views

Inner join on output of a subquery

We have Slot table which tells us about freetime for an employee between starttime and endtime. We need to find Slot which have freetime > 'x' mins. This could be either be a complete slot or it can ...
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2answers
145 views

Nontrivial joining a relation with itself [closed]

I am a philosopher and am doing my first steps in relational algebra. So here is a puzzle: Let say that we have a relation R with attributes 'R.a' and 'R.b'. Is it possible to make a renaming and ...
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0answers
285 views

How to get the hierarchy of particular employee using JPA spring boot?

I am trying to find a way to get the employee hierarchy in an organization using JPA and Spring boot. The problem is similar to the following link Similar Data Model If A reports to B and B reports ...
2
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1answer
41 views

Looking for help reporting duplicates and null marks

Someone over at StackOverflow suggested this might be the place to ask this. I hope this will question is proper for this forum. I am looking for suggestions / criticisms of alternative methods of ...
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3answers
492 views

Many-to-many tag filter query with a junction table get slower with more tags. Can it be faster?

Part 1 I have this query to find some videos containing all given tags. Here with tags 1,9,27,13,67 as an example. SELECT * FROM video v WHERE v.id IN ( SELECT tr1.vid as video_id FROM (SELECT ...
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2answers
736 views

Update using the value from the closest row

My table looks like this: ----------------------------------------- id | name | housename | houseno ----------------------------------------- 1 | John | John's House | 2/22 ---------...
4
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1answer
2k views

Joining multiple subqueries

I need a query that returns something in this format: pk id v1 v2 v3 v4 v5 ---------------------- ... pk1 id1 A1 A2 A3 A4 A5 pk6 id2 B1 B2 B3 B4 B5 ... My current data looks like this CREATE ...
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2answers
4k views

Filter one column by value in second column postgres

I'm constructing a large table that is pulling values from across the database. Two of the fields I want to include in the new table are stored in a single column in another table. I want to split ...
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1answer
2k views

Help on Self-Referential CTE SQL SERVER

I have this table below which is has a hierarchy to it where the number of levels vary, for this example I chose a subset with 7 levels. L_Key Parent Level P_Key ------------------------- 1393 ...
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1answer
67 views

Want to perform a function on a returned table on subset of rows

I have a query that takes 10 minutes to run (1.4 million rows and 15-ish joins), so I think the time isn't terrible. What I need from this is to effectively INNER JOIN on itself an additional column ...
5
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2answers
1k 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-...