CHAR
char (M) M字符，長(zhǎng)度是M*字符編碼長(zhǎng)度，M最大255。
驗(yàn)證如下：
| mysql> create table t1(name char(256)) default charset=utf8;ERROR 1074 (42000): Column length too big for column 'name' (max = 255); use BLOB or TEXT insteadmysql> create table t1(name char(255)) default charset=utf8;Query OK, 0 rows affected (0.06 sec)mysql> insert into t1 values(repeat('整',255));Query OK, 1 row affected (0.00 sec)mysql> select length(name),char_length(name) from t1;+--------------+-------------------+| length(name) | char_length(name) |+--------------+-------------------+| 765 | 255 |+--------------+-------------------+1 row in set (0.00 sec) |
VARCHAR
VARCHAR(M)，M同樣是字符，長(zhǎng)度是M*字符編碼長(zhǎng)度。它的限制比較特別，行的總長(zhǎng)度不能超過(guò)65535字節(jié)。
| mysql> create table t1(name varchar(65535));ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBsmysql> create table t1(name varchar(65534));ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBsmysql> create table t1(name varchar(65533));ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBsmysql> create table t1(name varchar(65532));Query OK, 0 rows affected (0.08 sec) |
注意，以上表的默認(rèn)字符集是latin1，字符長(zhǎng)度是1個(gè)字節(jié)，所以對(duì)于varchar，最大只能指定65532字節(jié)的長(zhǎng)度。
如果是指定utf8，則最多只能指定21844的長(zhǎng)度
| mysql> create table t1(name varchar(65532)) default charset=utf8;ERROR 1074 (42000): Column length too big for column 'name' (max = 21845); use BLOB or TEXT insteadmysql> create table t1(name varchar(21845)) default charset=utf8;ERROR 1118 (42000): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBsmysql> create table t1(name varchar(21844)) default charset=utf8;Query OK, 0 rows affected (0.07 sec) |
注意：行的長(zhǎng)度最大為65535，只是針對(duì)除blob，text以外的其它列。
