UTF8字符集下：
| SQL>create table test(id int auto_increment,name varchar(10),primary key(id));SQL>insert into test values(null,'1234567890');Query OK, 1 row affected (0.00 sec)SQL>insert into test values(null,'一二三四五六七八九十');Query OK, 1 row affected (0.00 sec)SQL>insert into test values(null,'abcdefghig');Query OK, 1 row affected (0.01 sec)SQL>insert into test values(null,12345678901);ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>insert into test values(null,'一二三四五六七八九十1');ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>insert into test values(null,'一二三四五六七八九十一');ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>select id,name,length(name),char_length(name) from test;+----+--------------------------------+--------------+-------------------+ | id | name | length(name) | char_length(name) | +----+--------------------------------+--------------+-------------------+ | 1 | 1234567890 | 10 | 10 | | 2 | 一二三四五六七八九十 | 30 | 10 | | 3 | abcdefghig | 10 | 10 | +----+--------------------------------+--------------+-------------------+ 3 rows in set (0.00 sec) |
GBK字符集下：
| SQL>create table test(id int auto_increment,name varchar(10),primary key(id));SQL>insert into test values(null,'1234567890');Query OK, 1 row affected (0.00 sec)SQL>insert into test values(null,'一二三四五六七八九十');Query OK, 1 row affected (0.00 sec)SQL>insert into test values(null,'abcdefghig');Query OK, 1 row affected (0.01 sec)SQL>insert into test values(null,12345678901);ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>insert into test values(null,'一二三四五六七八九十1');ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>insert into test values(null,'一二三四五六七八九十一');ERROR 1406 (22001): Data too long for column 'name' at row 1SQL>select id,name,length(name),char_length(name) from test;+----+----------------------+--------------+-------------------+ | id | name | length(name) | char_length(name) | +----+----------------------+--------------+-------------------+ | 1 | 1234567890 | 10 | 10 | | 2 | 一二三四五六七八九十 | 20 | 10 | | 3 | abcdefghig | 10 | 10 | +----+----------------------+--------------+-------------------+ 3 rows in set (0.00 sec) |
由此可見，varchar定義的長度的單位是字符，哪怕是1個多字節字符也是1個字符，如中文和英文字母都被當作1個字符來對待。
那么varchar能夠定義的最大長度是多少呢？這個和你當前所使用的字符集有關。拋開字符，其最大長度為65535字節(這是最大行大小，由所有列共享)，而放在不同的字符集下，能夠定義的最大長度就會有所不同，如UTF8下是21845。據說MySQL5中varchar的長度也為字符，而MySQL4中的則為字節，未經證實，感興趣的有環境可以自己測下。
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