1、长度不同

char是固定长度 0-255的任何值

varchar 是可变长度0-65535

2、检索时候不同

char在检索的时候列删除了尾部的空格，而varchar保留这些空格

a、创建表

mysql> create table vc (v varchar(4),c char(4));

Query OK, 0 rows affected (0.27 sec)

b、插入数据

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

Query OK, 1 row affected (0.01 sec)

mysql> commit;

Query OK, 0 rows affected (0.05 sec)

mysql> select * from vc;

+------+------+

| v    | c    |

+------+------+

| ab   | ab   |

+------+------+

1 row in set (0.00 sec)

c、查看长度

mysql> select length(v),length(c) from vc;

+-----------+-----------+

| length(v) | length(c) |

+-----------+-----------+

|         4 |         2 |

+-----------+-----------+

1 row in set (0.08 sec)

测试中间有空格是否被删除

mysql> insert into vc values('a bc','a bc');

Query OK, 1 row affected (0.02 sec)

mysql> select length(v),length(c) from vc;

+-----------+-----------+

| length(v) | length(c) |

+-----------+-----------+

|         4 |         4 |

+-----------+-----------+

中间有空格时 varchar 和char都不删除空格