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Questions tagged [natural-join]

A natural join is a relational operation that joins on the like-named attributes between tables

Natural join (⋈) is a binary operator that is written as (R⋈S) where R and S are relations. The result of the operation is the set of all combinations of tuples in R and S that have equal values on their common attribute names. The resulting relation has a heading consisting of the set-union of the attributes from R and S, i.e. there are no duplicate attribute names in the result.

If the joined relations have no attribute names in common then R⋈S is equivalent to R×S (Cartesian product).

The natural join of any relation, R, to itself is R (R⋈R = R).

The ISO Standard SQL syntax for natural join (R⋈S) is:

SELECT * FROM R NATURAL JOIN S;
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What is USING keyword in SQL Server 2008?

I know the beautiful usage of the SQL clause "USING": it is similar to NATURAL JOIN but you must detail the join columns; you can join more simply (and faster) the tables that have the same key and foreign key, and the output of queries doesn't…
Alberto
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Difficulties in understanding natural join

I'm having problems understanding the main point of natural join in database systems. According to the definition, the natural join selects the combination of 2 tables having the same values of columns whose names equal. My problem is: what if there…
doniyor
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Does natural join distribute over set-difference?

In other words, is it true that: r1 ⋈ (r2 - r3) = r1 ⋈ r2 - r1 ⋈ r3 where r1 r2 and r3 are relations If it isn't what is the example?
Eyal
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Natural Join -- Relational theory and SQL

This question comes from my readings of C.J Date's SQL and Relational Theory: How to Write Accurate SQL Code and looking up about joins on the internet (which includes coming across multiple posts here on NATURAL JOINs (and about SQL Server's lack…
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SQLite INNER JOIN - How to output only one of the common columns the two tables have

Let's say that I have two tables: lessons with columns: lessonID, name studentlessons with columns: lessonID, age I am trying to perform this action: SELECT lessons.*, studentlessons.* FROM studentlessons JOIN lessons WHERE…
stavros.3p
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How to do an algorithm complexity analysis for code

For a class I had to write a program that does stuff with tables. I did the hard part, but now I need to write an algorithm complexity analysis for it. I understand BASICALLY what this is, and I can apply it to simple things like a loop, but the…
Thomas
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Is Natural Join distributive over Union?

Given three relations R, S and T, is it true that: R ⋈ (S U T) = (R ⋈ S) U (R ⋈ T) If yes, can we prove it?
lebowski
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Remove Duplicates From JOIN

I'm currently learning databases in school right now, but unfortunately our teacher doesn't really enjoy helping or answering questions, at all. I'm currently working on a couple of Oracle DB exercises right now and I've come across one question I…
timn1
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SQL natural join POSTGRES

I'm not sure what kind of join I need as I'm not familiar with trying to overlap data in such a way or if it's even feasible. I have two tables which both share a similar set of data and are both related to a 3rd parent table thru Room_id. I have a…
holden
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Natural Join Implementation Python

I am working on implementing natural join in python. The first two lines show the tables attributes and the next two lines each tables' tuples or rows. Expected Output: [['A', 1, 'A', 'a', 'A'], ['A', 1, 'A', 'a', 'Y'], ['A', 1, 'Y', 'a', 'A'],…
user3264378
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Relational Algebra - Natural join - few basics

I have two basics questions regarding the natrual join. Suppose A is a relation, then: Is (A) natrual join (A) = A ? Is (A) natrual join (empty set) = A ? As far as I understand the answer to both questions is YES, am I right? NOTE : this is…
SyndicatorBBB
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How to do natural join when the common column have different names?

I need to do natural join on two tables named Customers and Addresses (relationship 1:1), the common column in those tables is the key- ID (according to that column the natural join will operate) . however- this Column in table Customer is called…
user2162278
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SQL Natural Join on Multiple Tables including nulls

Excuse my ignorance on this question if it is really simple but its driving me crazy and I have searched (tried and failed) different solutions from this site so here goes... I am using SQL 2008 and trying to pull results from 12 tables into a…
SQL Beginner
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What the Heck is wrong with my (not to complex) MySQL-Query?

I might be blind on both eyes, but iterating through a lot of versions and tries... Deleted the hyphenation and the AS statements... I always ended up with a parsing Error 1064 from my MySql5.1 Server. I really believe this is valid, SQL…
Andreas Kosmo
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SQL Query Issue - Natural Join and table naming

I'm running into some difficulty with a query for my databases class. Given the following schema: Customers (customerid, first_name, last_name, address, city, state, phone, status) Branches (branchno, address, city, state, phone,…
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