mysql二進制類型

因爲以前網站使用第三方登陸，QQ暱稱比較特殊，因此用二進制的字段類型存儲。

mysql二進制類型有：

BINARY

VARBINARY

TINYBLOB, BLOB, MEDIUMBLOB, and LONGBLOB

順便列一下各類數據類型的存儲範圍：

Storage Requirements for Numeric Types

Data Type	Storage Required
TINYINT	1 byte
SMALLINT	2 bytes
MEDIUMINT	3 bytes
INT, INTEGER	4 bytes
BIGINT	8 bytes
FLOAT(p)	4 bytes if 0 <= p <= 24, 8 bytes if 25 <= p <= 53
FLOAT	4 bytes
DOUBLE [PRECISION], REAL	8 bytes
DECIMAL(M,D), NUMERIC(M,D)	Varies; see following discussion
BIT(M)	approximately (M+7)/8 bytes

Storage Requirements for Date and Time Types

Data Type	Storage Required Before MySQL 5.6.4	Storage Required as of MySQL 5.6.4
YEAR	1 byte	1 byte
DATE	3 bytes	3 bytes
TIME	3 bytes	3 bytes + fractional seconds storage
DATETIME	8 bytes	5 bytes + fractional seconds storage
TIMESTAMP	4 bytes	4 bytes + fractional seconds storage

Storage Requirements for String Types

Data Type	Storage Required
CHAR(M)	M × w bytes, 0 <= M <= 255, where w is the number of bytes required for the maximum-length character in the character set. SeeSection 15.2.6.7, 「Physical Row Structure」 for information about CHAR data type storage requirements for InnoDB tables.
BINARY(M)	M bytes, 0 <= M <= 255
VARCHAR(M), VARBINARY(M)	L + 1 bytes if column values require 0 − 255 bytes, L + 2 bytes if values may require more than 255 bytes
TINYBLOB, TINYTEXT	L + 1 bytes, where L < 28
BLOB, TEXT	L + 2 bytes, where L < 216
MEDIUMBLOB, MEDIUMTEXT	L + 3 bytes, where L < 224
LONGBLOB, LONGTEXT	L + 4 bytes, where L < 232
ENUM('value1','value2',...)	1 or 2 bytes, depending on the number of enumeration values (65,535 values maximum)
SET('value1','value2',...)	1, 2, 3, 4, or 8 bytes, depending on the number of set members (64 members maximum)

參考：http://dev.mysql.com/doc/refman/5.7/en/data-types.html