Set operators have roots in the actual branch of mathematics – set algebra.
In the SQL context a set is a result of a query. Basic set operations are unions and intersections. They are available to us in the form of 4 operators:
INTERSECT. Let’s have a closer look at the first two.
UNION combines the results of 2 SQL queries together. There are a bunch of important features of
- result sets must have the same number of columns
- column types must match
- it filters out duplicated rows. The result of