Table 1.1: Selected data type representations 7
Data type Example Representation
Numeric data Integer 2-8 bytes 1
decimal(n) n bytes 2
Character data character (n) n or 2n bytes 3
CLOB (n)
Character Large OBject
n bytes 4
Binary data
(audio/visual)
Boolean (True/False) one bit 5
BLOB (n)
Binary Large OBject
n bytes 6
Notes:

  1. Depending on type of data: small integer - double precision numbers. 1 byte = 8 bits of storage space, which is the minimum addressable unit of storage.
  2. Decimal numbers are stored as characters, 1 digit per byte.
  3. Depends on the character set used. For example, both Chinese and Arabic characters require 16 representations.
  4. The maximum length of LOB (CLOB or BLOB) data is system dependent. Oracle's dbms currently supports 4 GB.
  5. If only one boolean type is used, the data will actually take up 1 byte.
  6. Note that audio/visual data can be very large, requiring up to 1GB for a 1-hour movie (in compressed MPEG format).
  7. Note that the names, number and maximum lengths of data types supported by a specific data management system may vary and change over time, making it necessary to consult the system documentation when implementing database systems.