MBA (General) - IV Semester, Information Technology and E-Business, Unit 2.1
Define Metadata, Indexes and Applications Metadata
Recall that a database is self describing
Metadata
Recall that a database is self describing
Metadata Data about data
Data that describe how user data are stored in
terms of table name, column name, data type, length, primary keys, etc.
Metadata are typically stored in System tables
or System Catalog and are typically only directly accessible by the DBMS or by
the system administrator.
Have a look at the Database Documentor feature
of MS Access (under the tools menu, choose Analyze and then Documentor).
This tool queries the system tables to give all
kinds of Metadata for tables, etc. in an MS Access database.
Indexes
In keeping with our desire to provide users
with several different views of data, indexes provide an alternate means of
accessing user data. Sorting and Searching
An index for our new banking example might
include the account numbers in a sorted order.
Indexes allow the database to access a record
without having to search through the entire table.
Updating data requires an extra step The index
must also be updated.
Example Index in a book consists of two things
A Keyword stored in order to point to the rest
of the information.
In the case of the book, the pointer is a page
number.
Applications Metadata
Many DBMS have storage facilities for forms,
reports, queries and other application components.
Applications Metadata is accessed via the
database development programs.
Example Look at the Documenter tool in MS
Access. It can also show metadata for Queries, Forms, Reports, etc.
