What does LEFT JOIN do?

SQLJunior~1 min read

LEFT JOIN returns all rows from the left table (the one listed first in the query), and only the matching rows from the right one.

If the right table has no match, NULL fills its place.

sql

SELECT *
FROM customers
LEFT JOIN orders
ON customers.id = orders.customer_id;

Here, every customer ends up in the result, and for those with no orders, the orders columns come back as NULL.

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