# 创建t1表,分别指明字段x为char类型，字段y为varchar类型

mysql> create table t1(x char(5),y varchar(4));

Query OK, 0 rows affected (0.16 sec)

# char存放的是5个字符，而varchar存4个字符

mysql> insert into t1 values('你瞅啥 ','你瞅啥 ');

Query OK, 1 row affected (0.01 sec)

# 在检索时char很不要脸地将自己浪费的2个字符给删掉了，装的好像自己没浪费过空间一样，而varchar很老实，存了多少，就显示多少

mysql> select x,char_length(x),y,char_length(y) from t1;

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

| x | char_length(x) | y | char_length(y) |

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

| 你瞅啥 | 3 | 你瞅啥 | 4 |

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

row in set (0.02 sec)

#略施小计，让char现原形

mysql> SET sql_mode = 'PAD_CHAR_TO_FULL_LENGTH';

Query OK, 0 rows affected (0.00 sec)

#查看当前mysql的mode模式

mysql> select @@sql_mode;

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

| @@sql_mode |

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

| PAD_CHAR_TO_FULL_LENGTH |

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

row in set (0.00 sec)

#原形毕露了吧。。。。

mysql> select x,char_length(x) y,char_length(y) from t1;

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

| x | y | char_length(y) |

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

| 你瞅啥 | 5 | 4 |

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

row in set (0.00 sec)

# 查看字节数

#char类型：3个中文字符+2个空格=11Bytes

#varchar类型:3个中文字符+1个空格=10Bytes

mysql> select x,length(x),y,length(y) from t1;

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

| x | length(x) | y | length(y) |

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

| 你瞅啥 | 11 | 你瞅啥 | 10 |

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

row in set (0.02 sec)