Python34_01-數據庫----數據庫基礎語法

數據庫基礎語法

1. 登陸和登出數據庫

1. 鏈接數據庫

mysql -uroot -pmysql

2. 退出數據庫

quit, exit, ctrl+D

 

2. 數據庫操做的sql語句

1. 顯示時間

select now();

2. 查看全部數據庫

show databases;

3. 建立數據庫(例如: python1)

create datsbase python1 charse=utf8;

4. 使用數據庫

use python1

5. 查看當前使用的數據庫

select database();

6. 刪除數據庫

drop database python1;

 

3. 表結構操做的sql語句

1. 查看數據庫中的全部表

show tables;

2. 建立表(例如: students表(id(無符號, 主鍵, 非空),姓名(字符串, 非空), 年齡(短整型, 非空, 默認爲0)))

create table students(id int unsigned primary key auto_increment not null, name varchar(30) notnull, age tinyint not null default 0);

3. 查看錶結構

desc students;

4. 修改表--添加字段

alter table students add birthday datetime default 0;

5. 修改表--修改字段, 不重命名

alter table students modify birthday date not null;

6. 修改表--修改字段, 重命名

alter table students change birthday birth date not null;

7. 修改表--刪除字段

alter table students drop birthday;

8. 查看錶建立語句

select create table students;

9. 查看庫建立語句

select create database python1;

10. 刪除表

drop table students;

11. 刪除庫

drop database pytohn1;

4. 表數據操做的sql語句

1. 增長--全列插入(向students表中增長列)

insert into students values(0, '張三', 18);

2. 增長--部分插入(向students表中增長name)

insert into students(name) values('張三')

3. 修改--全列修改

update students set name = '李四';

4. 修改--部分修改

update students set name = '李四' where id = 1;

5. 刪除--物理刪除

delect from students where id = 2;

6. 邏輯刪除

alter table students add id_delect bit default 0;

update studets det students.id_delect = 1 where id = 2;

select * from students where id_delect = 1;

7. 查詢--查詢全部列

select * from students;

8. 查詢指定列

select id, birth from students;

9. 字段順序(按年齡從大到小排序)

select * from students order by age desc;

10. 使用關鍵字as起別名

(給字段起別名) select id as i, birth as b from students;

(給表起別名) select s.id, s.birth from student as s;

11. 消除重複行

select distinct id from students;

12. where 條件查詢(比較, 邏輯, 模糊, 範圍, 空)

(比較) select * from students where age > 7;

(邏輯) select * from students where age > 5 and age < 7;

(模糊) select * from students where name like '黃%_'  ----(%替換任意個, _替換一個)

(範圍) select * from students where age in (1, 2, 3, 5) ----(不連續範圍)

(空) select * from students where age is not null;

13. between... and...連續範圍內

select * from students where age between 2 and 7;