数据查询

mysql-> select * from mysql_test.cust

　  　-> where cust_sex='M';

mysql-> select * from mysql_test.cust

　  　-> where cust_id between 903 and 912;

mysql-> select * from mysql_test.cust

　  　-> where cust_id in(903,906,908);

mysql-> select * from mysql_test.cust

　  　-> where cust_contact is null;  //is not null

mysql-> select studentNo,studentName 

　  　-> from tb_student

　　  -> where studentNo in(select studentNo from tb_score where score>80);   //通过外键联系起来

mysql-> select cust_address,cust_sex,count(*) as '人数'   //mysql 5.5版本的group by后面的字段必须和select的字段一致

　  　->  from mysql_test.cust

　　  ->  group by cust_address,cust_sex;

mysql-> select cust_address,cust_sex,count(*) as '人数'  //汇总

　  　->  from mysql_test.cust

　　  ->  group by cust_address,cust_sex

　　  ->  with rollup;

mysql-> select cust_name,cust_address

　  　->  from mysql_test.cust

　　  ->  group cust_name,cust_address

　　  ->  having count(*)<=3;

mysql-> select cust_name,cust_sex from mysql_test.cust

　  　->  order by cust_name desc,cust_sex desc;

mysql-> select cust_id,cust_name from mysql_test.cust

　  　->  order by cust_id

　　  ->  limit 4,3;   //默认从0开始 另一种形式: limit 3 offset 4;

练习:

(1)   select * from 图书

　　where 单价 between 50 and 60

　　order by 出版社,单价;

(2)  select 书名,借阅时间

　　from 图书,借阅,读者

　　where 姓名='王明' and 读者.借书证号=借阅.借书证号 and 借阅.图书编号=图书.图书编号;

(3)  select 出版社,max(单价),min(单价),avg(单价)

　　from 图书

　　group by 出版社;