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Matching Data From Multiple Tables with SQL LEFT JOIN

Reading time 1 min
Published Aug 9, 2017
Updated Oct 3, 2019

SQL LEFT JOIN: Main Tips

  • LEFT JOIN can be called LEFT OUTER JOIN.
  • If there is no match, the result is NULL.

SQL LEFT JOIN Keyword

Returns all information from the left table (mytable1), and the matched information from the right table (mytable2).

Syntax of SQL LEFT JOIN

Example
SELECT column_name(s)
FROM mytable1
LEFT JOIN mytable2 ON mytable1.column_name = mytable2.column_name;
Theory is great, but we recommend digging deeper!

Demo Database

This is demo example from the "Developers" table in the database:

ID Name City Country
1 Tom Kurkutis New York USA
2 Ana Fernandez London UK
3 Antonio Indigo Paris France
4 Aarav Kaelin Delhi India
5 Andrew Tumota Miami USA

This is demo example from the "Orders" table in the database:

ID Customer_ID Employee_ID
20408 2 7
20409 2 5
85471 1 3
75864 5 8

SQL LEFT JOIN: Example

In this example, we'll return all developers, and their orders:

Example
SELECT Developers.Name, Customer_orders.ID
FROM Developers
LEFT JOIN Customer_orders ON Developers.ID = Customer_orders.customer_id
ORDER BY Developers.Name;

Note: LEFT JOIN returns all the left table rows from (Developers), even if finding matches in the right table (Orders).