4 ms·
Yes, I know about USING, and you probably know about the one big issue it has; if you add a column name with the same name to some table included, then you get
by JoelJacobson 6y ago
Yes, I know about USING, and you probably know about the one big issue it has; if you add a column name with the same name to some table included, then you get an error due to the ambiguity.
Example:
SELECT
language.name,
COUNT(*)
FROM rental
JOIN customer USING (customer_id)
JOIN address USING (address_id)
JOIN city USING (city_id)
JOIN country USING (country_id)
JOIN inventory USING (inventory_id)
JOIN film USING (film_id)
JOIN language USING (language_id)
WHERE country.country = 'Sweden'
GROUP BY language.name
Works fine, but if we do
ALTER TABLE rental ADD address_id integer;
Then we get
ERROR: common column name "address_id" appears more than once in left table
The foreign key based join approach doesn't suffer from this problem, since there which columns to join on is explicit and stable.