varchar 和char的区别

[whdugh]

mysql> create table vc(v varchar(4),c char(4));
Query OK, 0 rows affected (0.08 sec)

mysql> desc vc;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| v | varchar(4) | YES | | NULL | |
| c | char(4) | YES | | NULL | |
+-------+------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> insert into vc values('ab','ab');
Query OK, 1 row affected (0.03 sec)

mysql> select length(v),length(c) from vc;
+-----------+-----------+
| length(v) | length(c) |
+-----------+-----------+
| 2 | 2 |
+-----------+-----------+
1 row in set (0.00 sec)

mysql> select concat(v,'+'),concat(c,'+') from vc;
+---------------+---------------+
| concat(v,'+') | concat(c,'+') |
+---------------+---------------+
| ab+ | ab+ |
+---------------+---------------+
1 row in set (0.03 sec)

mysql>


这样看varchar与char没有区别啊，为什么长度都是2啊，varchar(4)长度不应该是4 吗？还有varchar不是应该保留空格的吗？这是怎么回事啊

[「已注销」]

你这样 想

insert  into  vc values('ab ','ab ');

[「已注销」]

然后

select length(a),length(b) from vc;

[benluobo]

varchar(4)长度不应该是4 吗？还有varchar不是应该保留空格的吗？ varchar(4)是指最长的长度为4，属于变长字段，保留空格的是char

[whdugh]

引用 1 楼 benluobobo 的回复:

varchar(4)长度不应该是4 吗？还有varchar不是应该保留空格的吗？ varchar(4)是指最长的长度为4，属于变长字段，保留空格的是char

mysql> select length(v),length(c) from vc; +-----------+-----------+ | length(v) | length(c) | +-----------+-----------+ | 2 | 2 | +-----------+-----------+ 1 row in set (0.00 sec) length(v) 不是应该为4吗？ mysql> select concat(v,'+'),concat(c,'+') from vc; +---------------+---------------+ | concat(v,'+') | concat(c,'+') | +---------------+---------------+ | ab+ | ab+ | +---------------+---------------+ 应该是这样的结果对吧： mysql> select concat(v,'+'),concat(c,'+') from vc; +---------------+---------------+ | concat(v,'+') | concat(c,'+') | +---------------+---------------+ | ab+ | ab + | +---------------+---------------+