例項是最好的說明，所以,廢話少說，看錶看例子~

mysql> show create table test_varchar_utf8\G
*************************** 1. row ***************************
       Table: test_varchar_utf8
Create Table: CREATE TABLE `test_varchar_utf8` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(12) NOT NULL,
  PRIMARY KEY (`id
 
`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
#這裡name欄位資料型別為varchar長度指定為12，這個12究竟是位元組數還是字元數呢？

#嘗試插入幾組不同長度的值
mysql> insert into test_varchar_utf8(name)values('12345678901');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('123456789012
 
');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('1234567890123');
ERROR 1406 (22001): Data too long for column 'name' at row 1
#發現，對於非中文字串，可以插入包含12個字元以及小於12個字元的字串，當大於12個字元時報錯。
#因為對於非中文的字元一個字元佔用一個位元組，所以，至此還不能說明varchar(n)中的n究竟代表位元組數還是字元數

#試著插入另外一組值包含中文字元的字串
mysql> insert into
 
 test_varchar_utf8(name)values('你');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好麼');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好麼親');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好麼親愛的');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好麼親愛的你好麼親愛的');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_varchar_utf8(name)values('你好麼親愛的你好麼親愛的你');
ERROR 1406 (22001): Data too long for column 'name' at row 1
#發現，對於中文字串，也可以插入包含12個字元以及小於12個字元的字串，當大於12個字元時報錯。
#因為對於中文的字元一個字元佔用三個位元組，所以，說明varchar(n)中的n代表字元數而非位元組數。

#對於char型別，可以做類似的實驗，結論相同
mysql> show create table test_char_utf8\G
*************************** 1. row ***************************
       Table: test_char_utf8
Create Table: CREATE TABLE `test_char_utf8` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` char(12) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

mysql> insert into test_char_utf8(name)values('12345678901');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('123456789012');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('1234567890123');
ERROR 1406 (22001): Data too long for column 'name' at row 1

mysql> insert into test_char_utf8(name)values('你好');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('你好麼');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('你好麼親');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('你好麼親愛的');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('你好麼親愛的你好麼親愛的');
Query OK, 1 row affected (0.00 sec)

mysql> insert into test_char_utf8(name)values('你好麼親愛的你好麼親愛的你');
ERROR 1406 (22001): Data too long for column 'name' at row 1

#下面的查詢顯示了utf8字符集下中文字元與非中文字元所佔用的位元組數對比
mysql> select id,name,length(name),char_length(name)  from test_varchar_utf8;
+----+--------------------------------------+--------------+-------------------+
| id | name                                 | length(name) | char_length(name) |
+----+--------------------------------------+--------------+-------------------+
|  1 | 12345678901                          |           11 |                11 |
|  2 | 123456789012                         |           12 |                12 |
|  3 | 你                                   |            3 |                 1 |
|  4 | 你好                                 |            6 |                 2 |
|  5 | 你好麼                               |            9 |                 3 |
|  6 | 你好麼親                             |           12 |                 4 |
|  7 | 你好麼親愛的                         |           18 |                 6 |
|  8 | 你好麼親愛的你好麼親愛的             |           36 |                12 |
+----+--------------------------------------+--------------+-------------------+
8 rows in set (0.00 sec)

mysql> select id,name,length(name),char_length(name)  from test_char_utf8;
+----+--------------------------------------+--------------+-------------------+
| id | name                                 | length(name) | char_length(name) |
+----+--------------------------------------+--------------+-------------------+
|  1 | 12345678901                          |           11 |                11 |
|  2 | 123456789012                         |           12 |                12 |
|  3 | 你好                                 |            6 |                 2 |
|  4 | 你好麼                               |            9 |                 3 |
|  5 | 你好麼親                             |           12 |                 4 |
|  6 | 你好麼親愛的                         |           18 |                 6 |
|  7 | 你好麼親愛的你好麼親愛的             |           36 |                12 |
+----+--------------------------------------+--------------+-------------------+
7 rows in set (0.00 sec)

如果你把例子從頭到尾看了下來，那麼你已經深刻理解了，也就無需我在做什麼總結了。是的你對了，(n)表示字元數！