Final answer:
Performing an outer join involves combining rows from two tables and returning all the rows from one table along with the matching rows from the other. An example with a 'movie' table would be using a LEFT JOIN to include all movies, irrespective of whether they have a matching director in the 'director' table.
Step-by-step explanation:
An outer join in SQL is used to combine rows from two or more tables. Unlike an inner join, where only the rows with matching values in both tables are returned, an outer join will return all rows from one table and the matched rows from the joined tables. If there is no match, the result is NULL on the side that does not have a match.
To illustrate an outer join with a 'movie' table, we can consider that we are joining it with another table named 'director'. Here's how you can perform a left outer join, which will return all movies, including those without a director associated:
SELECT movie.title, director.name
FROM movie
LEFT JOIN director
ON movie.director_id = director.id;
In this example, the LEFT JOIN keyword indicates that we want all records from the 'movie' table, and the matched records from the 'director' table. The result will include all movies, and for those movies with a director in the 'director' table, it will also show the director's name.
It's important to note that there are different types of outer joins: LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN. Each of these will give you a different result set depending on your requirements.