Slideshow:
When do you use database addresses
(that identify block/record stored on disks)
Data stored on disk will always use database addresses to reference other records
Example on when to use database addresses
When an employee record references another (supervisor) employee record:
Common situation
when we need to use database addresses
Index file records will always reference a data record:
- Database Address:
- Database Address =
an address used to identify
data (block/record)
stored on
disk
- Database Address =
an address used to identify
data (block/record)
stored on
disk
- How/when to use a
database address:
- When a record x need to
refer to
another record y,
we can store:
- the database address of y inside x
Example:
- When a record x need to
refer to
another record y,
we can store:
- Example usage 1: reference to
your supervisor
- Employee "John"
has the supervisor
employee Frank
- Employee "John"
has the supervisor
employee Frank
- Example usage 2: index files
-
Index files are
constructed to
speed up access
to
the data file
(We will study index files in the next chapter)
- Index files need to use
database addresses to
locate the records:
-
Index files are
constructed to
speed up access
to
the data file