SQL Database:

So, an SQL database is one whose symbols are organized into a collection of tables. Now, shows an SQL table as the current value of an SQL variable, ENROLMENT, but in that  connection there are two important points to be made right away. First, the term  table  variable isn't  used in SQL for its counterpart of relation variables. Instead, base relvars are normally referred to as  base tables, virtual relvars as  views  (or  viewed tables)  and those terms are used in the international  standard. Secondly, not every SQL table can be the value of a base table or view. As we shall soon see, table variables and the tables assigned to them are subject to several deviations from relational theory; tables that cannot be assigned to a variable are subject to even more deviations.