The WITH COMPRESSION attribute was added for CHARACTER columns because of the change to the Unicode character representation format. Unicode characters uniformly require two bytes for each character. For existing Microsoft Jet databases that contain predominately character data, this could mean that the database file would nearly double in size when converted to the Microsoft Access database engine format. However, Unicode representation of many character sets, those formerly denoted as Single-Byte Character Sets (SBCS), can easily be compressed to a single byte. If you define a CHARACTER column with this attribute, data will automatically be compressed as it is stored and uncompressed when retrieved from the column.