删除索引：drop index idxname

　　注：索引是不可更改的，想更改必须删除重新建。

32.说明：

　　创建视图：create view viewname as select statement

　　删除视图：drop view

viewname

33.说明：几个简单的基本的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

31、简单查询

select name from bbc where population>=200000000; --查询显示出人口不小于2亿的国家名字

select name ,(gdp/population)'人均GDP' from bbc where population>=200000000; --人口不小于200000000国家名称及人均gdp

select name , round((populatio/1000000))'人口数（百万）' from bbc where name in(south asia);

select name,popultion from bbc where name ='France', 'Germany', 'Italy'; --查询出france,germany,italy三国的人口数

select name from bbc where name like '%united%'查询出国家名称包括united字符的的所有国家名称；

表获得诺贝尔奖

select yr,subject winner from nobel where yr = 1950; --显示1950年获得诺贝尔奖的人.的所有信息

select winner from nobel where yr =1962; --1962文学奖获得者

select yr,subject from nodel where winner ='albert einstin'; --显示'Albert Einstein'获奖的年份和奖项．

select winner from nodel where yr>=2000 and subject = '和平奖';--2000年以来（包含2000年）和平奖的得主．

select * from nodel where yr between 1980 and 1989 and subject = '文学奖'; --1980到 1989间文学奖获得者的所有信息

select *from nodel where winner=('Theodore Roosevelt', 'Woodrow Wilson', 'Jed Bartlet', 'Jimmy Carter');

select winner from nodel where winner like 'john%'