查
select distinct Company,Ordername from Orders where city = "Beijing" or address = "Sanltun" order by city,address DESC
改
update Person set Address = "Zhongshan 23",city = "Nanjing" where Lastname = "vilan"
增
insert into Person(Lastname,Address) values('Wilson',‘Champs')
删
Delete * from Person where Lastname = "Vilon"
常见词
TOP前，like(_, [], %)通配符，in类似or，between...and...，as别名
union合并，select into备份，index索引，drop != truncate删，
alter table... add/drop column...增/删列，
约束
not null，unique, primary key, foreign key, check, default,
select funtion() from Table
group by...having...
其他
逗号，= join。left join右可空，right join左可空，
where != on，用join语句要用on
单个view可改，复合view不可改。