转自：http://stackoverflow.com/questions/5414551/what-is-it-exactly-a-blob-in-a-dbms-context
BLOB :
BLOB (Binary Large Object) is a large object data type in the database system. BLOB could store a large chunk of data, document types and even media files like audio or video files. BLOB fields allocate space only whenever the content in the field is utilized. BLOB allocates spaces in Giga Bytes.
USAGE OF BLOB :
You can write a binary large object (BLOB) to a database as either binary or character data, depending on the type of field at your data source. To write a BLOB value to your database, issue the appropriate INSERT or UPDATE statement and pass the BLOB value as an input parameter. If your BLOB is stored as text, such as a SQL Server text field, you can pass the BLOB as a string parameter. If the BLOB is stored in binary format, such as a SQL Server image field, you can pass an array of type byte as a binary parameter.
有关链接：<a href = "http://stackoverflow.com/questions/211895/storing-documents-as-blobs-in-a-database-any-disadvantages">Storing documents as BLOB in Database - Any disadvantages ?</a>
