LIST-CLASSES — List classes for tables in SQL database.
Function
test
	      a function used to filter the search. By default, identity is used which
	      will return all classes.
	    
root-class
	      specifies the root class to the search. By default,
	      standard-db-object is used which
	      is the root for all view classes.
	    
databaseThe database to search for view classes. This will default to the value of *default-database*.
classesList of view classes.
Returns a list of all the View Classes which have been
      defined in the Lisp session and are connected to
      database and which descended from the
      class root-class and which satisfy the
      function test.
      
(list-classes)
=> (#<clsql-sys::standard-db-class big> #<clsql-sys::standard-db-class employee-address>
    #<clsql-sys::standard-db-class address> #<clsql-sys::standard-db-class company> 
    #<clsql-sys::standard-db-class employee>)
(list-classes :test #'(lambda (c) (> (length (symbol-name (class-name c))) 3)))
=> (#<clsql-sys::standard-db-class employee-address> #<clsql-sys::standard-db-class address>
    #<clsql-sys::standard-db-class company> #<clsql-sys::standard-db-class employee>)