Joins Galore

Kevin Feasel

2017-01-13

Syntax

Lukas Eder has a comprehensive guide to joining data using SQL:

Alternative syntaxes: NATURAL JOIN

An more extreme and much less useful form of "EQUI" JOIN is the NATURAL JOIN clause. The previous example could be further “improved” by replacing USING by NATURAL JOIN like this:

SELECT *
FROM actor
NATURAL JOIN film_actor
NATURAL JOIN film

Notice how we no longer need to specify any JOIN criteria, because a NATURAL JOIN will automatically take all the columns that share the same name from both tables that it joins and place them in a “hidden” USING clause. As we’ve seen before, as primary keys and foreign keys have the same column name, this appears quite useful.

There is a high likelihood that you will learn at least one new thing here; for example, check out lateral joins (which SQL Server practitioners know as something else).

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