ROLLBACK — Roll back modifications made in the current transaction.Function
databaseA database object. This will default to the value of *default-database*.
If database, which defaults to
      *default-database*, is currently within the
      scope of a transaction, rolls back changes made since the
      transaction began.
      
(in-transaction-p)
=> NIL
(select [*] :from [foo] :field-names nil)
=> NIL
(start-transaction)
=> NIL 
(in-transaction-p)
=> T
(insert-records :into [foo] :av-pairs '(([bar] 1) ([baz] "one")))
=> 
(select [*] :from [foo] :field-names nil)
=> ((1 "one"))
(rollback)
=> NIL 
(in-transaction-p)
=> NIL
(select [*] :from [foo] :field-names nil)
=> NIL
      
       Changes made within the scope of the current transaction are
       reverted in the underlying database and the transaction level
       of database is reset.  
        The transaction level of database which
        indicates whether a transaction has been initiated by a call to 
        start-transaction since the last call to 
        rollback or commit. 
      
        Signals an error of type sql-database-error
        if database is not a database object. A
        warning of type sql-warning is signalled if
        there is no transaction in progress.