MySQL基础知识六

1.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 

2.添加主键： Alter table tabname add primary key(col) 
 删除主键： Alter table tabname drop primary key(col) 

3.创建索引：create [unique] index idxname on tabname(col….) 
删除索引：drop index idxname 

4.基本的sql语句 
选择：select * from table1 where 范围 
插入：insert into table1(field1,field2) values(value1,value2) 
删除：delete from table1 where 范围 
更新：update table1 set field1=value1 where 范围 
查找：select * from table1 where field1 like '%value1%' ---like的语法很精妙，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(field1) as minvalue from table1