blob 数据类型

blob数据类型官方定义

• TINYBLOB

  A BLOB column with a maximum length of 255 (2⁸ − 1) bytes. Each TINYBLOB value is stored using a 1-byte length prefix that indicates the number of bytes in the value.

• TINYTEXT [CHARACTER SET *charset_name*] [COLLATE *collation_name*]

  A TEXT column with a maximum length of 255 (2⁸ − 1) characters. The effective maximum length is less if the value contains multibyte characters. Each TINYTEXT value is stored using a 1-byte length prefix that indicates the number of bytes in the value.

• BLOB[(*M*)]

  A BLOB column with a maximum length of 65,535 (2¹⁶ − 1) bytes. Each BLOB value is stored using a 2-byte length prefix that indicates the number of bytes in the value.

  An optional length M can be given for this type. If this is done, MySQL creates the column as the smallest BLOB type large enough to hold values M bytes long.

• TEXT[(*M*)] [CHARACTER SET *charset_name*] [COLLATE *collation_name*]

  A TEXT column with a maximum length of 65,535 (2¹⁶ − 1) characters. The effective maximum length is less if the value contains multibyte characters. Each TEXT value is stored using a 2-byte length prefix that indicates the number of bytes in the value.

  An optional length M can be given for this type. If this is done, MySQL creates the column as the smallest TEXT type large enough to hold values M characters long.

• MEDIUMBLOB

  A BLOB column with a maximum length of 16,777,215 (2²⁴ − 1) bytes. Each MEDIUMBLOB value is stored using a 3-byte length prefix that indicates the number of bytes in the value.

• MEDIUMTEXT [CHARACTER SET *charset_name*] [COLLATE *collation_name*]

  A TEXT column with a maximum length of 16,777,215 (2²⁴ − 1) characters. The effective maximum length is less if the value contains multibyte characters. Each MEDIUMTEXT value is stored using a 3-byte length prefix that indicates the number of bytes in the value.

• LONGBLOB

  A BLOB column with a maximum length of 4,294,967,295 or 4GB (2³² − 1) bytes. The effective maximum length of LONGBLOBcolumns depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGBLOBvalue is stored using a 4-byte length prefix that indicates the number of bytes in the value.