标签：set 0.00 简单 使用 rows sec mysql NULL MySql
在终端中操作数据库
Linux中Mysql是区分大小写的，win不区分大小写
数据库
1. show databases查看数据库服务器中数据库
输入命令行后需要输入;作为结束
2. use <databasesname>选择一个数据库进行操作
mysql> use test
Database changed
3. exit退出数据服务器
4.create database <name>数据库服务器中创建数据库
mysql> create database study
-> ;
Query OK, 1 row affected (0.05 sec)
mysql> show databases
-> ;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| study |
| test |
+--------------------+
4 rows in set (0.00 sec)
mysql>
5. show tables查看数据库中的数据表
mysql> show tables
-> ;
Empty set (0.00 sec)
mysql>
6. drop database<datebasename>删除数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| study |
| test |
+--------------------+
4 rows in set (0.00 sec)
mysql> drop database test;
Query OK, 0 rows affected (0.03 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| study |
+--------------------+
3 rows in set (0.00 sec)
数据表
1. create table <tablename>(datename datatype(size)，...)创建数据表
表名字中参数为原始名和元素大小
mysql> create table pet(name varchar(20), owner varchar(20), species varchar(20), sex char(1), birth date, death date);
Query OK, 0 rows affected (0.31 sec)
mysql> show tables
-> ;
+-----------------+
| Tables_in_study |
+-----------------+
| pet |
+-----------------+
1 row in set (0.00 sec)
如何设置字段不能为NULL
- 创建时：
在字段类型之后加上
NOT NULL即可
create table pet(name varchar(20) NOT NULL)
2.describe <tablename>查看数据表的结构
mysql> describe pet
-> ;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| owner | varchar(20) | YES | | NULL | |
| species | varchar(20) | YES | | NULL | |
| sex | char(1) | YES | | NULL | |
| birth | date | YES | | NULL | |
| death | date | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
6 rows in set (0.03 sec)
- Filed 字段名
- Type 字段类型
- Null 是否可以为空
- Key 约束条件
- Default 默认值
- Extra 额外的
3. select <Field> from <tablename>查看数据表中的记录
Field表示字段名字。通过这个参数可以进行筛选出需要的子段。
*是全部字段名
mysql> select * from pet
-> ;
Empty set (0.00 sec)
select 添加查找条件
mysql> select * from pet where name = "Tom" and sex = "f";
+------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+------+-------+---------+------+------------+-------+
| Tom | Diane | ham | f | 1999-03-30 | NULL |
+------+-------+---------+------+------------+-------+
1 row in set (0.00 sec)
限制查找结果的个数limit x
mysql> select * from user limit 2
-> ;
+----------+--------+
| username | pass |
+----------+--------+
| dawd | 213123 |
| dokpd | 213123 |
+----------+--------+
2 rows in set (0.02 sec)
mysql> select * from user limit 1;
+----------+--------+
| username | pass |
+----------+--------+
| dawd | 213123 |
+----------+--------+
1 row in set (0.01 sec)
4.insert into <tablename>往数据表中添加数据记录
mysql> insert into pet
-> values ("Tom", "Diane", "ham", "f", "1999-03-30",NULL);
Query OK, 1 row affected (0.11 sec)
输入命令行后需要补齐输入的信息 value (. . .)
mysql> select * from pet
-> ;
+------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+------+-------+---------+------+------------+-------+
| Tom | Diane | ham | f | 1999-03-30 | NULL |
+------+-------+---------+------+------------+-------+
1 row in set (0.00 sec)
5. drop table <tablename>删除数据表
mysql> show tables;
+-----------------+
| Tables_in_study |
+-----------------+
| pet |
| tmp |
+-----------------+
2 rows in set (0.00 sec)
mysql> drop table tmp;
Query OK, 0 rows affected (0.65 sec)
mysql> show tables;
+-----------------+
| Tables_in_study |
+-----------------+
| pet |
+-----------------+
1 row in set (0.00 sec)
6. update tablename set Field = newValue where conditon...更新满足条件的值
mysql> select * from pet
-> ;
+------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+------+-------+---------+------+------------+-------+
| Tom | Diane | ham | f | 1999-03-30 | NULL |
| Jack | Diane | ham | f | 1999-03-30 | NULL |
+------+-------+---------+------+------------+-------+
2 rows in set (0.00 sec)
mysql> update pet set name = "Li" where name = "Tom";
Query OK, 1 row affected (0.12 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from pet
-> ;
+------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+------+-------+---------+------+------------+-------+
| Li | Diane | ham | f | 1999-03-30 | NULL |
| Jack | Diane | ham | f | 1999-03-30 | NULL |
+------+-------+---------+------+------------+-------+
2 rows in set (0.00 sec)
7. delete from <tablename>清除数据表中的所有记录
mysql> select * from user;
+----------+------+
| username | pass |
+----------+------+
| 21344 | 1234 |
| Tom | 1234 |
+----------+------+
2 rows in set (0.00 sec)
mysql> delete from user;
Query OK, 2 rows affected (0.02 sec)
mysql> select * from user;
Empty set (0.00 sec)
条件删除
mysql> select * from user;
+----------+--------+
| username | pass |
+----------+--------+
| awdad | 1234 |
| dawd | 213123 |
| dawda | 1234 |
| dokpd | 213123 |
| jack | 1234 |
| tmp | 1234 |
+----------+--------+
6 rows in set (0.00 sec)
mysql> delete from user where pass = 1234;
Query OK, 4 rows affected (0.15 sec)
mysql> select * from user;
+----------+--------+
| username | pass |
+----------+--------+
| dawd | 213123 |
| dokpd | 213123 |
+----------+--------+
2 rows in set (0.00 sec)
标签：set,0.00,简单,使用,rows,sec,mysql,NULL,MySql 来源： https://blog.csdn.net/weixin_53475254/article/details/120474226
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