What is the difference between union and join?

Question

What is the difference between the SQL keywords union and join?

Answer 1

The UNION operator is used to combine the result-set of two or more SELECT statements.

The JOIN keyword is used in an SQL statement to query data from two or more tables, based on a relationship between certain columns in these tables.

The tutorials on these two topics (linked to above) on w3schools.com go into further detail.

Answer 2

Think of joins as horizontal and unions as vertical