--if object_id('guestbook') is null
--CREATE TABLE guestbook (id int PRIMARY KEY, visitor VARCHAR(40),comments TEXT,entrydate DATETIME)
--insert into guestbook values(3,'a','123','2016-05-12')
--insert into guestbook values(4,'a','1234','2016-05-12')
--insert into guestbook values(5,'a','12345','2016-05-12')
--if object_id('guestbook') is not null
--drop table guestbook
--if exists(select * from sysobjects where name='guestbook')
--drop table guestbook
--update guestbook set visitor='b' where id='4'
--select * from guestbook
--delete guestbook where id='3'
--truncate table guestbook
