PostgreSQL中character、character varing、text数据类型的区别

左手的ㄟ右手 2022-06-06 10:19 379阅读 0赞

*  PostgreSQL中charactercharacter varingtext数据类型的区别
    
     *  一测试环境
        
         *  测试表
            
             *  看不出有何异同
             *  发现character4 在不足4位时会补空格其他则不会
             *  发现character4不能超过4个字符
             *  发现character varing4也不能超过4个字符
             *  字符无限制

# PostgreSQL中character、character varing、text数据类型的区别 #

## 一.测试环境: ##

*  PostgreSQL 9.6.5
 *  pgAdmin 4.1.0

### 测试表: ###

test表:

<table> 
 <thead> 
  <tr> 
   <th align="left">ch4</th> 
   <th align="left">chvar4</th> 
   <th align="left">chvar</th> 
   <th align="left">tx</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">character(4)</td> 
   <td align="left">character varing(4)</td> 
   <td align="left">character varing</td> 
   <td align="left">text</td> 
  </tr> 
 </tbody> 
</table>

测试SQL:

#### **0.看不出有何异同:** ####

insert into test(ch4,chvar4,chvar,tx) values('ab','ab','ab','ab');
    select * from test;

![这里写图片描述][SouthEast]

#### **1.发现character(4) 在不足4位时会补空格。其他则不会。** ####

![这里写图片描述][SouthEast 1]

#### **2.发现character(4)不能超过4个字符。** ####

insert into test(ch4,chvar4,chvar,tx) values ('abcde','abcde','abcde','abcde');

![这里写图片描述][SouthEast 2]

ERROR: value too long for type character(4)
     ********** Error ********** 
    ERROR: value too long for type character(4) 
    SQL state: 22001

#### **3.发现character varing(4)也不能超过4个字符。** ####

insert into test(chvar4,chvar,tx) values ('abcde','abcde','abcde');

![这里写图片描述][SouthEast 3]

ERROR: value too long for type character varying(4)
     ********** Error ********** 
    ERROR: value too long for type character varying(4) 
    SQL state: 22001

#### **4.字符无限制** ####

insert into test(chvar,tx) values ('abcde','abcde');
    select * from test;

![这里写图片描述][SouthEast 4]

参考资料:  
\\< PostgreSQL9从零开始学 > : ISBN-9787302316732  
[https://www.postgresql.org/docs/9.6/static/index.html][https_www.postgresql.org_docs_9.6_static_index.html]

[SouthEast]: /images/20220606/e92b96f8c20c4413bfce5a51f5fc8d65.png
[SouthEast 1]: /images/20220606/4a3fb86b76e84f6a90c71c597f805850.png
[SouthEast 2]: /images/20220606/7e4cc4479c5d4b6ea32314e0a383b935.png
[SouthEast 3]: /images/20220606/6ec461da5de5467480b7e8f7699a3503.png
[SouthEast 4]: /images/20220606/5a1922ff101f4e86a234b853aa941e49.png
[https_www.postgresql.org_docs_9.6_static_index.html]: https://www.postgresql.org/docs/9.6/static/index.html