常用SQL语句说明

1.创建数据库
CREATE DATABASE database-name
2.删除数据库
drop database dbname 
3.备份sql server
----创建 备份数据的device
USE master
EXEC sp_addumpdevice 'disk','testBack','c:mssql7backup\MyNwind_1.dat'
-----开始备份
BACKUP DATABASE pubs TO testBack
4.创建新表
create table tabname(col1 type1[not null] [primary key],col2 type2[not null],......)
根据已有的表创建新表：
A:create table tab_new like tab_old(使用旧表创建新表)
B:create table tab_new as select col1,col2....from tab_old definition only
5.删除新表
drop table tabname 
6.增加一个列
Alter table tabname add column col type
注：列增加后将不能删除。DB2中列加上后数据类型也不能改变，唯一能改变的是增加varchar类型的长度。
7.添加主键：Alter table tabname ass prinmary key(col)
   删除主键：Alter table tabname drop primary key(col)
8.创建索引：create [unique] index idxname on tabname(col......)
注：索引是不可更改的，想更改必须删除重新建。
9.创建视图：create view viewname as select statement 
   删除视图：drop view viewname
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10.几个简单的基本sql语句
选择：select * from table1 where 范围
插入：insert into table1(field1,fied2) values(value1,value2)
删除：delete from table1 where 范围
更新：update table1 set fied1 =value1 where 范围
查找：select * from table1 where field1 like ' %value1%' ---like的语法很精妙，请自查资料！
排序：select * from table1 order by field1,field2[desc]
总数：select count as totalcount from table1
求和：select sum(field1) as sumvalue from table1
平均：select avg(field1) as avgvalue from table1
最大：select max(field1) as maxvalue from table1
最小：select min(filed1) as minvalue from table1