All kinds of PostgreSQL join methods are useful and get selected based on the nature of the query, data, join clause, etc. INNER JOIN is used massively in PostgreSQL query statements, INNER JOIN only displays the rows that match the two joined tables on a particular column. How NATURAL JOIN works in PostgreSQL? PostgreSQL JOINs are used for retrieving data from more than one tables. PostgreSQL natural join. With JOINs, it is possible for us to combine the SELECT and JOIN statements into a single statement. In PostgreSQL, the row has a value by the name of the table. Following is the syntax for a Natural Join: * FROM b ) AS b ON (a.a1 = b.b1); Using a row comparison. In general, "trying it out" should not be used as a valid approach to conclude particular behavior is guaranteed or "the default" -- there are numerous SET options that can influence T-SQL behavior, for example, even though this happens to not be the case for JOIN.Your code is fine to illustrate the behavior, but is not authoritative. Assuming you mean just writing a JOIN without any other keywords, like this: SELECT * FROM TABLE1 JOIN TABLE2 ON TABLE1.A = TABLE2.A You would be doing an INNER JOIN by default. Suppose that you want to perform a full outer join of two tables: A and B. Syntax of PostgreSQL Natural Join. Suppose: table1 LEFT JOIN table2 JOIN CONDITION . Even easier though then forcing a false value for which we can compare, is to compare the row. In-case the query is not performing as expected, i.e. The following illustrates the syntax of the FULL OUTER JOIN: SELECT * FROM A FULL [OUTER] JOIN B on A.id = B.id; In this syntax, the OUTER keyword is optional. Introduction to the PostgreSQL FULL OUTER JOIN. A NATURAL JOIN can be a LEFT JOIN, INNER JOIN or RIGHT JOIN, but the type of join must be specified in the connection or PostgreSQL will use the INNER JOIN operation by default.. A JOIN condition is added to the statement, and all rows that meet the conditions are returned. SELECT a.a1, b.b1, CASE WHEN b.cond IS NULL THEN 100 ELSE b.b2 END AS b2 FROM a LEFT OUTER JOIN ( SELECT true AS cond, b. join methods are not selected as expected then, the user can play around with different plan configuration parameters available and see if something is missing. The PostgreSQL LEFT JOIN joins two tables and fetches rows based on a condition, which is matching in both tables and the unmatched rows will also be available from the table written before the JOIN clause. The PostgreSQL uses the INNER JOIN by default if we do not define a name of join explicitly as INNER JOIN, LEFT JOIN, or RIGHT JOIN. By default, PostgreSQL will use the INNER JOIN operation. presto:default> SELECT count(*) FROM postgres.public.t1 x INNER JOIN kala.public.t1 y ON x.c1 = y.c1; _col0 ----- 1 (1 row) Query 20170731_122315_00004_s3nte, FINISHED, 1 node Splits: 67 total, 67 done (100.00%) 0:00 [3 rows, 0B] [12 rows/s, 0B/s] Pros: Lot of datasources, good SQL support, good documentation, monitoring dashboard How to Add a Default Value to a Column in PostgreSQL-- Example: Orders have a default total of 0 cents alter table orders alter column total_cents set default 0; -- Example: Items are available by default alter table items alter column available set default true; A NATURAL JOIN groups records together based on similarities with column values found in other tables. And it can be used with LEFT JOIN, INNER JOIN or RIGHT JOIN, but the type of join must be defined in the joining or PostgreSQL will use the INNER JOIN operation by default. 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