day38 mysql的相关配置/破解密码/库增删改查/表增删改查/记录的增删改查/库详细操作/数据类型/字符类型/枚举与几何类型

数据库的基本概念:

1、数据库是什么？
    数据库本质就是一个C/S的套接字软件
    常见的数据库：
        关系型：
            mysql
            mariadb
            oracle
            db2
            sqlserver

        非关系：
            存取数据都是以key:value
            mongodb
            redis
            memcache


2、数据库相关概念
    数据库服务器：运行有数据库管理软件的计算机
    数据库管理软件mysql：就是一个套接字服务端
    库：就是一个文件夹
    表：就是一个文件
    记录：就相当于文件中的一行内容（抽取事物一系列典型的特征拼到一起，）
    数据：用于记录现实世界中的某种状态

数据库安装步骤

#1、下载：MySQL Community Server 5.7.16
http://dev.mysql.com/downloads/mysql/

#2、解压
如果想要让MySQL安装在指定目录，那么就将解压后的文件夹移动到指定目录，如：C:mysql-5.7.16-winx64

#3、添加环境变量
【右键计算机】--》【属性】--》【高级系统设置】--》【高级】--》【环境变量】--》【在第二个内容框中找到 变量名为Path 的一行，双击】 --> 【将MySQL的bin目录路径追加到变值值中，用 ； 分割】
 
#4、初始化
mysqld --initialize-insecure

#5、启动MySQL服务
mysqld # 启动MySQL服务

#6、启动MySQL客户端并连接MySQL服务
mysql -u root -p # 连接MySQL服务器

安装
my.ini配置文件
mysqld服务端
client 客户端全局性配置
mysql 客户端

　　

配置文件管理

pass

破解密码

mysql(客户端)  mysqld(服务端)

客户端登录

mysql -uroot -p

管理员设置密码相关密码(视频有相关介绍)

破解密码的两种方法

方法一: 暴力破解法   将(E:mysql56datamysql)路径下的所有文件删除，适用于刚刚安装没有多少内容的数据库

net start mysql 正常启动mysql

net stop mysql 把服务端给停掉

quit是退出客户端

方法二:mysqld --skip-grant-tables (跳过授权表)

updata mysql.user set password="123"

但凡权限修改,flush privileges

mysql的相关破解步骤 

#1、关闭mysql
net stop mysql

#2、重新启动
mysqld --skip-grant-tables
#3
mysql -uroot -p

update mysql.user set password=password("egon123") where user="root" and host="localhost";
flush privileges; #password(代表表当中的一个字段，password()代表mysql的一个功能)
                  #where是条件的意思userhost="localhost"代表本地账号
　　　　　　　　　　 #flush privileges  刷新权限

#4、关闭mysql，正常启动 net start mysql

 数据类型1的上课相关笔记

数据类型1
mysql> create table t3(x tinyint);
Query OK, 0 rows affected (0.02 sec)

mysql> desc t3;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| x     | tinyint(4) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
1 row in set (0.02 sec)

mysql> show create table t3;
+-------+-----------------------------------------------------------------------
-----------------+
| Table | Create Table
                 |
+-------+-----------------------------------------------------------------------
-----------------+
| t3    | CREATE TABLE `t3` (
  `x` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+-----------------------------------------------------------------------
-----------------+
1 row in set (0.00 sec)

mysql> insert into t3 values(-1);
Query OK, 1 row affected (0.00 sec)

mysql> select*from t3;
+------+
| x    |
+------+
|   -1 |
+------+
1 row in set (0.00 sec)

mysql> insert into t3 values(130);
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> select*from t3;
+------+
| x    |
+------+
|   -1 |
|  127 |
+------+
2 rows in set (0.00 sec)

mysql> insert into t1 values('128');
ERROR 1136 (21S01): Column count doesn't match value count at row 1
mysql> insert into t3 values('136');
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> select*from t3;
+------+
| x    |
+------+
|   -1 |
|  127 |
|  127 |
+------+
3 rows in set (0.00 sec)

mysql>  select @@sql_mode;
+------------------------+
| @@sql_mode             |
+------------------------+
| NO_ENGINE_SUBSTITUTION |
+------------------------+
1 row in set (0.00 sec)

mysql> set global sql_mode="strict_trans_table";
ERROR 1231 (42000): Variable 'sql_mode' can't be set to the value of 'strict_tra
ns_table'
mysql> set global sql_mode="srtict_trans_tables";
ERROR 1231 (42000): Variable 'sql_mode' can't be set to the value of 'srtict_tra
ns_tables'
mysql> set global sql_mode="strict_trans_tables";
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

C:UsersAdministrator>mysql
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 2
Server version: 5.6.24 MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> select @@sql_mode;
+---------------------+
| @@sql_mode          |
+---------------------+
| STRICT_TRANS_TABLES |
+---------------------+
1 row in set (0.00 sec)

mysql> use sb1;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'sb1'
mysql> use db1;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'db1'
mysql> use sb1;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'sb1'
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| test               |
+--------------------+
2 rows in set (0.00 sec)

mysql> use sb1;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'sb1'
mysql> mysql -uroot -p;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'mysql
 -uroot -p' at line 1
mysql> mysql -uroot -p;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'mysql
 -uroot -p' at line 1
mysql> mysql -uroot -p
    -> c;
ERROR:
No query specified

mysql> c
mysql> quit
Bye

C:UsersAdministrator>mysql -uroot -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 3
Server version: 5.6.24 MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> use sb1;
Database changed
mysql> des t3;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near 'des t
3' at line 1
mysql> desc t3;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| x     | tinyint(4) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
1 row in set (0.01 sec)

mysql> select*from t3;
+------+
| x    |
+------+
|   -1 |
|  127 |
|  127 |
+------+
3 rows in set (0.00 sec)

mysql> insert into t3 values(128);
ERROR 1264 (22003): Out of range value for column 'x' at row 1
mysql> create table t4(x tinyint unsigned);
Query OK, 0 rows affected (0.02 sec)

mysql> desc t4;
+-------+---------------------+------+-----+---------+-------+
| Field | Type                | Null | Key | Default | Extra |
+-------+---------------------+------+-----+---------+-------+
| x     | tinyint(3) unsigned | YES  |     | NULL    |       |
+-------+---------------------+------+-----+---------+-------+
1 row in set (0.04 sec)

mysql> insert into t4 values(255);
Query OK, 1 row affected (0.00 sec)

mysql> insert into t4 values(-1);
ERROR 1264 (22003): Out of range value for column 'x' at row 1
mysql> create table t5(id int(1));
Query OK, 0 rows affected (0.03 sec)

mysql> desc t5;
+-------+--------+------+-----+---------+-------+
| Field | Type   | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| id    | int(1) | YES  |     | NULL    |       |
+-------+--------+------+-----+---------+-------+
1 row in set (0.04 sec)

mysql> insert t5 values(300000);
Query OK, 1 row affected (0.00 sec)

mysql> insert t5 values(9876543210123);
ERROR 1264 (22003): Out of range value for column 'id' at row 1
mysql> insert t5 values(9876543210);
ERROR 1264 (22003): Out of range value for column 'id' at row 1
mysql> insert t5 values(987654321);
Query OK, 1 row affected (0.00 sec)

mysql> select*from t5;
+-----------+
| id        |
+-----------+
|    300000 |
| 987654321 |
+-----------+
2 rows in set (0.00 sec)

mysql> create table t6(id int(5));
Query OK, 0 rows affected (0.02 sec)

mysql> insert into t6 values(2147483648);
ERROR 1264 (22003): Out of range value for column 'id' at row 1
mysql> select*from t6;
Empty set (0.00 sec)

mysql> insert into t6 values(2147483647);
Query OK, 1 row affected (0.00 sec)

mysql> insert into t6 values(13);
Query OK, 1 row affected (0.00 sec)

mysql> select*from t6;
+------------+
| id         |
+------------+
| 2147483647 |
|         13 |
+------------+
2 rows in set (0.00 sec)

mysql> drop table t6;
Query OK, 0 rows affected (0.02 sec)

mysql> create table t6(id int(5) zerofill);
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t6 values(1);
Query OK, 1 row affected (0.00 sec)

mysql> insert into t6 values(13);
Query OK, 1 row affected (0.00 sec)

mysql> select*from t6;
+-------+
| id    |
+-------+
| 00001 |
| 00013 |
+-------+
2 rows in set (0.00 sec)

mysql> insert into t6 values(13132122);
Query OK, 1 row affected (0.00 sec)

mysql> select*from t6;
+----------+
| id       |
+----------+
|    00001 |
|    00013 |
| 13132122 |
+----------+
3 rows in set (0.00 sec)

mysql> create table t7(id int);
Query OK, 0 rows affected (0.02 sec)

mysql> desc t7;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
1 row in set (0.03 sec)


数据类型2
mysql> create table t8 (x float(255,30));
Query OK, 0 rows affected (0.01 sec)

mysql> create table t9 (x double(255,30));
Query OK, 0 rows affected (0.01 sec)

mysql> create table t10(x decimal(65,30));
Query OK, 0 rows affected (0.03 sec)

mysql> desc t8;
+-------+---------------+------+-----+---------+-------+
| Field | Type          | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| x     | float(255,30) | YES  |     | NULL    |       | #精度最低
+-------+---------------+------+-----+---------+-------+
1 row in set (0.03 sec)

mysql> desc t9;
+-------+----------------+------+-----+---------+-------+
| Field | Type           | Null | Key | Default | Extra |
+-------+----------------+------+-----+---------+-------+
| x     | double(255,30) | YES  |     | NULL    |       | #精度第二
+-------+----------------+------+-----+---------+-------+
1 row in set (0.02 sec)

mysql> desc t10;
+-------+----------------+------+-----+---------+-------+
| Field | Type           | Null | Key | Default | Extra |
+-------+----------------+------+-----+---------+-------+
| x     | decimal(65,30) | YES  |     | NULL    |       |  #精度最高
+-------+----------------+------+-----+---------+-------+
1 row in set (0.01 sec)

mysql> insert into t8 values(1.1111111111111111111111111111111);
Query OK, 1 row affected (0.00 sec)

mysql> insert into t9 values(1.1111111111111111111111111111111);
Query OK, 1 row affected (0.00 sec)

mysql> insert into t10 values(1.1111111111111111111111111111111);
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> select*from t8;
+----------------------------------+
| x                                |
+----------------------------------+
| 1.111111164093017600000000000000 |
+----------------------------------+
1 row in set (0.00 sec)

mysql> select*from t9;
+----------------------------------+
| x                                |
+----------------------------------+
| 1.111111111111111200000000000000 |
+----------------------------------+
1 row in set (0.00 sec)

mysql> select*from t10;
+----------------------------------+
| x                                |
+----------------------------------+
| 1.111111111111111111111111111111 |
+----------------------------------+
1 row in set (0.00 sec)

数据类型3
mysql> create table student(
    ->     id int primary key auto_increment,
    ->     name char(16),
    ->     born_year year,
    ->     birth date,
    ->     class_time time,
    ->     reg_time datetime
    -> );
Query OK, 0 rows affected (0.02 sec)

mysql> desc student;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| name       | char(16) | YES  |     | NULL    |                |
| born_year  | year(4)  | YES  |     | NULL    |                |
| birth      | date     | YES  |     | NULL    |                |
| class_time | time     | YES  |     | NULL    |                |
| reg_time   | datetime | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+
6 rows in set (0.03 sec)

mysql> create table student(
    ->     id int primary key auto_increment,
    ->     name char(16),
    ->     born_year year,
    ->     birth date,
    ->     class_time time,
    ->     reg_time datetime
    -> );
ERROR 1050 (42S01): Table 'student' already exists
mysql> insert into student(name,born_year,birth,class_time,reg_time) values
    -> ('egon1',now(),now(),now(),now());#now截取当前的时间
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql>
mysql> insert into student(name,born_year,birth,class_time,reg_time) values
    -> ('egon1',2000,20001111,now(),now());
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into student(name,born_year,birth,class_time,reg_time) values
    -> ('egon1',2000,'2000-11-11',083000,now());
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into student(name,born_year,birth,class_time,reg_time) values
    -> ('egon1',2000,'2000-11-11',"08:30:00",20171111111111);
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into student(name,born_year,birth,class_time,reg_time) values
    -> ('egon1',2000,'2000-11-11',"08:30:00","2017-11-11 11:11:11");
Query OK, 1 row affected (0.00 sec)

mysql> select*from student;
+----+-------+-----------+------------+------------+---------------------+
| id | name  | born_year | birth      | class_time | reg_time            |
+----+-------+-----------+------------+------------+---------------------+
|  1 | egon1 |      2018 | 2018-07-24 | 09:35:13   | 2018-07-24 09:35:13 |
|  2 | egon1 |      2000 | 2000-11-11 | 09:35:13   | 2018-07-24 09:35:13 |
|  3 | egon1 |      2000 | 2000-11-11 | 08:30:00   | 2018-07-24 09:35:13 |
|  4 | egon1 |      2000 | 2000-11-11 | 08:30:00   | 2017-11-11 11:11:11 |
|  5 | egon1 |      2000 | 2000-11-11 | 08:30:00   | 2017-11-11 11:11:11 |
+----+-------+-----------+------------+------------+---------------------+
5 rows in set (0.00 sec)

mysql> create table t11(x timestamp);
Query OK, 0 rows affected (0.02 sec)

mysql> desc t11;
+-------+-----------+------+-----+-------------------+--------------------------
---+
| Field | Type      | Null | Key | Default           | Extra
   |
+-------+-----------+------+-----+-------------------+--------------------------
---+
| x     | timestamp | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTA
MP |
+-------+-----------+------+-----+-------------------+--------------------------
---+
1 row in set (0.03 sec)

mysql> insert into t11 values();
Query OK, 1 row affected (0.00 sec)

mysql> select*from t11;
+---------------------+
| x                   |
+---------------------+
| 2018-07-24 09:40:14 |
+---------------------+
1 row in set (0.00 sec)

mysql> create table t12(x datetime);
Query OK, 0 rows affected (0.02 sec)

mysql> desc t12;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| x     | datetime | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+
1 row in set (0.01 sec)

mysql> insert into t12 values();
Query OK, 1 row affected (0.00 sec)

mysql> select*from t12;
+------+
| x    |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

mysql> drop table t12;
Query OK, 0 rows affected (0.01 sec)

mysql> create table t12(x datetime not null default now());
Query OK, 0 rows affected (0.02 sec)

mysql> insert into t12 values();
Query OK, 1 row affected (0.00 sec)

mysql> insert into t12 values();
Query OK, 1 row affected (0.00 sec)

mysql> insert into t12 values();
Query OK, 1 row affected (0.00 sec)

mysql> select*from t;
ERROR 1146 (42S02): Table 'sb2.t' doesn't exist
mysql> select*from t12;
+---------------------+
| x                   |
+---------------------+
| 2018-07-24 09:45:50 |
| 2018-07-24 09:45:52 |
| 2018-07-24 09:45:53 |
+---------------------+
3 rows in set (0.00 sec)

　

文件：表
    切换文件夹
        use db1;
        select database(); 查看当前所在的库
    增
        create table t1(id int,name char);  #char 就是字符串  mysql称为字符
        create table db1.t1(id int,name char);
    删
        drop table t1;
    改
        alter table t1 add age int;
        alter table t1 modify name char(15);#仅只能改数据类型 最大传15个字符
        alter table t1 change name NAME char(15);#数据名字和类型都可以改
        alter table t1 drop age;

    查
        show tables;
        show create table t1;
        desc t1; 查看表结构

文件内的一行行内容：记录
    增
        insert into t1(id,name) values
        (1,'egon'),
        (2,'lxx'),
        (3,'alex');

    删
        delete from db1.t1 where id >= 2;

        create table t2(id int primary key auto_incremnt,name char(15));
        insert into t2(name) values
        ('egon'),
        ('lxx'),
        ('wxx'),
        ('axx');

        清空表应该使用：
            truncate t2;
    改
        update db1.t1 set name='lxx_dsb' where id=2;
    查
        select id from db1.t1;
        select id,name from t1;
        select name,id from t1;
        select * from t1;
        select * from t1 where id >= 2;

SQL语言主要用于存取数据、查询数据、更新数据和管理关系数据库系统,SQL语言由IBM开发。SQL语言分为3种类型：
#1、DDL语句    数据库定义语言： 数据库、表、视图、索引、存储过程，例如CREATE DROP ALTER
#2、DML语句    数据库操纵语言： 插入数据INSERT、删除数据DELETE、更新数据UPDATE、查询数据SELECT
#3、DCL语句    数据库控制语言： 例如控制用户的访问权限GRANT、REVOKE

库相关操作

查看数据库
show databases;
show create database db1;
select database();
选择数据库
USE 数据库名
删除数据库
DROP DATABASE 数据库名;
修改数据库
alter database db1 charset utf8;

数据类型

一、创建表的完整语法
#语法：
create table 库名.表名(
    字段名1 类型[(宽度) 约束条件],#中括号里面的代表可有可无
    字段名2 类型[(宽度) 约束条件],
    字段名3 类型[(宽度) 约束条件]
);
约束条件：是在数据类型之外对字段附加的额外的限制

#注意：
1、最后一个字段之后不能加逗号
2. 在同一张表中，字段名是不能相同
3. 宽度和约束条件可选，字段名和类型是必须的

二、数据类型
#1、整型：默认是有符号的
create table t3(x tinyint);

ps：修改sql_mode为严格模式，必须重启客户端才能生效
    set global sql_mode="strict_trans_tables";
    select @@sql_mode;

create table t4(x tinyint unsigned);

# 强调：整型类型后面的宽度限制的根本不是存储宽度，限制的是显示宽度
create table t5(id int(1));
create table t6(id int(5));

#2、浮点型：
float(255,30)
double(255,30)
decimal(65,30)

create table t8(x float(255,30));
create table t9(x double(255,30));
create table t10(x decimal(65,30));

insert into t8 values(1.111111111111111111111111111111);
insert into t9 values(1.111111111111111111111111111111);
insert into t10 values(1.111111111111111111111111111111);


3、日期类型
year 1999
date 1999-11-11
time 08:30:00
datetime/timestamp 1999-11-11 08:30:00

create table student(
    id int primary key auto_increment,
    name char(16),
    born_year year,
    birth date,
    class_time time,
    reg_time datetime
);
insert into student(name,born_year,birth,class_time,reg_time) values
('egon1',now(),now(),now(),now());#now截取当前的时间

insert into student(name,born_year,birth,class_time,reg_time) values
('egon1',2000,20001111,now(),now());

insert into student(name,born_year,birth,class_time,reg_time) values
('egon1',2000,'2000-11-11',083000,now());

insert into student(name,born_year,birth,class_time,reg_time) values
('egon1',2000,'2000-11-11',"08:30:00",20171111111111);

insert into student(name,born_year,birth,class_time,reg_time) values
('egon1',2000,'2000-11-11',"08:30:00","2017-11-11 11:11:11");

create table t11(x timestamp);
create table t12(x datetime not null default now());


4、字符类型
# 注意：宽度指限制的是字符个数
char：定长
    char(5)

varchar：变长
    varchar(5)

相同点：宽度指的都是最大存储的字符个数，超过了都无法正常存储
不同点：
    char(5):
        'm'--->'m    '5个字符   前4个是空格

    varchar(5)
        'm'--->'m'1个字符

set global sql_mode="strict_trans_tables,PAD_CHAR_TO_FULL_LENGTH";#填充字符串到最完整的长度

注意：mysql在查询时针对where 字段="值    "会忽略掉右面的空格，即where 字段="值"
如果时like模糊匹配就不会忽略右面的空格了

char(5)
egon |axx  |lxx  |fm   |

varchar(5)
1bytes+egon|1bytes+axx|1bytes+lxx|1bytes+fm|

# 宽度相关练习
mysql> create table t13(x char(5));
Query OK, 0 rows affected (0.20 sec)

mysql> create table t14(x varchar(5));
Query OK, 0 rows affected (0.27 sec)

mysql>
mysql>
mysql> insert into t13 values('xxxxxx');
ERROR 1406 (22001): Data too long for column 'x' at row 1
mysql> insert into t14 values('xxxxxx');
ERROR 1406 (22001): Data too long for column 'x' at row 1


5、枚举与集合类型
枚举enum('a','b','c'):多选一
集合set('a','b','c'):多选多

create table emp(
    name varchar(15),
    sex enum('male','female','unkown'),
    hobbies set('read','music','yinshi','play')
);

insert into emp values
('zhangming','xxx','xxxx');


mysql> insert into emp values('zhangming','female','read,play');
Query OK, 1 row affected (0.03 sec)

mysql> select * from emp;
+-----------+--------+-----------+
| name      | sex    | hobbies   |
+-----------+--------+-----------+
| zhangming | female | read,play |
+-----------+--------+-----------+
1 row in set (0.00 sec)
三、约束条件

为什么用vachar呢?

大多数情况下用varchar更省空间，但是用varchar不是因为更省空间的问题，因为现在的存储
越来越便宜，是因为数据存在硬盘，查询从硬盘经过IO读到内存里面去的，如果数据量小
就能经过更小的IO将数据读到内存，所以基于这点考虑应高用varchar