LONGBLOB

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

URL: http://dev.mysql.com/doc/refman/5.1/en/string-type-overview.html

