Certainly! A LEFT JOIN, also known as a LEFT OUTER JOIN, is a type of join in SQL that allows you to retrieve all rows from the left table, and any matching rows from the right table. If there is no match, NULL values are returned for right table's columns.
Here is an example to illustrate how a LEFT JOIN works:
Suppose you have two tables: `customers` and `orders`. The `customers` table has the following columns:
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`id | name | city ----+-------+--------- 1 | Alice | New York 2 | Bob | Los Angeles 3 | Eve | Chicago`
The `orders` table has the following columns:
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`id | customer_id | product | quantity ----+-------------+---------------+---------- 1 | 1 | iPhone | 2 2 | 3 | MacBook | 1 3 | 2 | iMac | 3 4 | 2 | Magic Mouse | 1 5 | 1 | Apple Watch | 1`
If you want to retrieve all customers and their orders (if any), you can use a LEFT JOIN as follows:
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`SELECT c.*, o.* FROM customers c LEFT JOIN orders o ON c.id = o.customer_id`
This will return the following result:
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`c.id | c.name | c.city | o.id | o.customer_id | o.product | o.quantity ------+---------+-----------+-------+----------------+-----------------+------------ 1 | Alice | New York | 1 | 1 | iPhone | 2 1 | Alice | New York | 5 | 1 | Apple Watch | 1 2 | Bob | Los Angeles| 3 | 2 | iMac | 3 2 | Bob | Los Angeles| 4 | 2 | Magic Mouse | 1 3 | Eve | Chicago | 2 | 3 | MacBook | 1`
I hope this helps! Let me know if you have any questions.
