mysql查询表基本操作

Posted 2020-07-12 社会主义虫不胖

数据库表的创建
create table <表名>
(
<列名> <数据类型及长度> [not null],
<列名> <数据类型及长度>,
...
<列名> <数据类型及长度>
)
删除表
drop table <表名>

导入导出数据
把表变成sql代码
备份与还原

增，删，改，查 CRUD

添加：
insert into <表名>[(列1,列2....)] values(<‘值1‘>，[‘值2‘])
注意：
1.列与值要匹配（数量，类型，次序）
2.列可以省掉，但值必须与表中的总列数和列的次序完全对应。
3.自增长列，不能省掉自增列，给自增列赋个‘‘

 

delete from car where code=‘c001‘
delete from car where brand=‘b001‘ or brand=‘b004‘
delete from car where brand=‘b001‘ || brand=‘b004‘
delete from car where brand=‘b007‘ && price>50
delete from car where brand=‘b007‘ and price>50

<> !=

更新
update <表名> set <列=值>[,列=值...] where .....
update info set sex=‘1‘ where code=‘p003‘
update info set sex=‘0‘,nation=‘n004‘,birthday=‘1999-9-9‘ where code=‘p001‘
update car set price=price * 0.9 where price > 30
update car set price =price * 0.95 where (brand=‘b006‘ || brand=‘b005‘)&&price>30

 

查询
select * from 表名
select 列名1,列名2... from 表名 --投影
select * from 表名 where 条件 --筛选

1.等值与不等值
select * from car where code=‘c001‘;
select * from car where code != ‘c001‘;
select * from car where price > 30;
--下面的都是范围
select * from car where price >=30 && price <=50;
select * from car where price between 30 and 50
select * from car where brand=‘b002‘ || brand=‘b004‘ || brand=‘b006‘
select * from car where brand in (‘b002‘,‘b004‘,‘b006‘)

2.模糊查
select * from car where name like ‘宝马%‘ %--任意多个任意字符
select * from car where name like ‘%5%‘
select * from car where name like ‘%型‘
select * from car where name like ‘__5%‘ _ -- 一个任意字符

3.排序
select * from 表名 where .... order by 列名 [ASC/DESC],列名[asc/desc]....

select * from car order by price desc
select * from car order by brand desc,price asc

保护数据：
获得数据库添加权限
grant insert
on constomers
to Mary

获取数据库检索权限
grant update,select
on constomers
to Mary
解除权限
revoke inse rt
on constomers
from mary