Check out example codes for "postgres join". It will help you in understanding the concepts better.
Code Example 1
-- This is in postgreSQL -- We have tableA and tableB, x is primary key in tableA and also -- a foreign key in tableB as y SELECT * FROM tableA JOIN tableB ON tableA.x = tableB.y; -- This will select all the columns from both tables that share a key
Code Example 2
SELECT * FROM weather INNER JOIN cities ON (weather.city = cities.name);
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