**LEFT JOIN** returns all records from the left table and matching records from the right table. For records with no matching, it completes the fields with **NULL**. For example, let's select all albums joined with songs ids with **LEFT JOIN**:

SELECT albums.title, songs.id
FROM albums 
LEFT JOIN songs ON songs.album_id = albums.id

On the diagram for this query, we can see that not all albums have songs in a table, so absent fields are autocompleted with NULL. Similarly, we can see in the result query: some albums have empty id's for the songs, because there are no songs for these albums.

If you're an expert in creating queries for a single table, improve your knowledge! Let's start accessing and manipulating two and more tables. During the course, you'll learn how to work with special statements, what is the join and how to use it, and also will practice a lot!

We shall take a look at the database we'll work with and how we can create a query inside another query.

Learn how to join and work with multiple tables.

Try creating queries with no limits on how you should do that. Use all your knowledge from previous chapters!

SQL Left & Right Join

Soluzione

SQL Left & Right Join

Soluzione