Left Join - SQL Programming

A left join keeps every row from the left table, even when the right side has no match.

Program

Play the query to keep a customer with no order.

left_join.sql

CREATE TABLE customers (id INTEGER, name TEXT);
CREATE TABLE orders (id INTEGER, customer_id INTEGER, total INTEGER);
INSERT INTO customers VALUES (1, 'Ada'), (2, 'Lin'), (3, 'Mia');
INSERT INTO orders VALUES (101, 1, 30), (102, 2, 12);
SELECT customers.name, orders.total FROM customers LEFT JOIN orders ON customers.id = orders.customer_id ORDER BY customers.id;

LEFT JOIN `LEFT JOIN` preserves the left table's rows.

NULL Missing right-side values appear as `NULL`.

outer join Left joins are a common outer-join form.