sql基本操做之增删改查

1. 显示数据库 show databases;

show databases;

2. 显示当前数据库

select current_database();

3. 建立数据库

create database db_name;

4. 选择某个数据库

use db_name;

5. 显示当前数据库下的表

show tables;

6. 建立表 create table

create table if not exists my_test(
   id INT UNSIGNED AUTO_INCREMENT,
   name_people VARCHAR(40) NOT NULL,
     submission_time DATETIME,
   PRIMARY KEY(id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

7. 描述表结构DESC或者DESCRIBE、show columns from

DESC my_test;
SHOW COLUMNS FROM my_test; #显示表结构

8. 插入数据 insert into

INSERT my_test(
    id,
    name_people,
    submission_time
)
VALUES
    (1, 'Mary', NOW());

9 .查询 select

select * from my_test;
select name_people from my_test;
select name_peole from my_test where id=1;

 

 

10. 删除一条记录 delete

delete from my_test where id=1;

11. 删除表中的全部记录，可是保存原来的表结构

delete from my_test;

12. 更新表的某一列 update

UPDATE my_test SET name_people = '陛下' WHERE id=1

13. 更新多列数据，用 ',' 逗号隔开

UPDATE my_test SET name_people = '将军', submission_time = NOW() WHERE id=1

 14. 增长新列 alter，而后update

ALTER table my_test add name_adress VARCHAR(50) not null;
update my_test set name_adress='北京';

 15. 复制另外一张表的数据和表结构，来新建表 create，使用as关键词

CREATE TABLE my_test_copy AS SELECT * FROM  my_test;
SELECT * from my_test_copy;

 

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