Greenplum Database SQL Joins: Overview and Demo

The five major types of joins that are discussed on this video include:

• Inner join: Inner joins are possibly the most common type of joins. The resulting data set is obtained by combining two tables on a common column. Each row of the left table is compared against each row of the right table. All matching rows are returned as part of the result set. An equijoin is an inner join that uses only equality comparisons in the join predicate.
• Left outer joins: Left outer joins return all of the rows from the left table even if there is no matching row in the right table. It also returns matching rows from the right table. Rows in the right table that do not match are not included as part of the result set.
• Right outer joins: Right outer joins return all of the rows from the right table even if there is no matching row in the left table. It also returns the matching rows from the left table.
• Full outer joins: Full outer join returns all rows from both tables where there is a match and returns NULL for rows that do not have a match.
• Cross joins: Cross join returns the Cartesian product of rows from tables in the join. The resulting data set consists of a combination of each row in the left table with each row in the right table. Two tables, each with five rows, will produce a resulting data set that contains twenty-five rows.