Set operations

Set is one of the most basic concepts in mathematics and it is very important in computer science as well. One of the main applications in computer science is in databases, which are the roots of most applications. Sets are used in query design and processing. When we create a query to retrieve a set of data in a relational database (Oracle, Microsoft SQL Server, MySQL, and so on), we design the query using set notation and the database will also return a set of data. When we create an SQL query, we can specify whether we want to retrieve all the data from a table or only a subset. We can also retrieve data that is common to two tables, data that exists only in one table (and not in the other table), or data that exists in both tables (among other operations). These operations are known in the SQL world as joins, and the base of SQL joins are set operations.

Note

To learn more about SQL join operations, please read at http://www.sql-join.com/sql-join-types.

We can perform the...