JOIN clause allows for the return of results from more than one table by joining them together with other results based on common column values specified using an
INNER JOIN is the default
JOIN and it will only return results matching the condition specified by
An outer join will combine rows from different tables even if the join condition is not met. In a
LEFT JOIN, every row in the left table is returned in the result set, and if the join condition is not met, then
NULL values are used to fill in the columns from the right table.
CROSS JOIN Clause
CROSS JOIN clause is used to combine each row from one table with each row from another in the result set. This
JOIN is helpful for creating all possible combinations for the records (rows) in two tables.
The given query will select the
pants_color columns from the result set, which will contain all combinations of combining the rows in the
pants tables. If there are 3 different shirt colors in the
shirts table and 5 different pants colors in the
pants table then the result set will contain 3 x 5 = 15 rows.
UNION clause is used to combine results that appear from multiple
SELECT statements and filter duplicates.
For example, given a
first_names table with a column
name containing rows of data “James” and “Hermione”, and a
last_names table with a column
name containing rows of data “James”, “Hermione” and “Cassidy”, the result of this query would contain three
names: “Cassidy”, “James”, and “Hermione”.
WITH clause stores the result of a query in a temporary table (
temporary_movies) using an alias.
Multiple temporary tables can be defined with one instance of the