Data Selection Using SQL
Joining two or more tables together is the best relational database usage. You relate the tables using the WHERE clause. The equal sign (=) in a query only retrieves records that have exact match. This is an example of the inner join or equijoin. Query the employees name and their department name from employee and department tables.
This is an example of a Cartesian product.
Query the department number and their total, average, min, and max salaries for each department.