Sunday, 24 May 2020

Database Management Systems (DBMS) Question Bank 01

DBMS question bank - why database administrators do not create index on every attribute of every relational table?

Question:


Why database administrators typically do NOT create an index on every single attribute of every single relation?


Answer:

  • Indexes are separate tables. They consume extra space - In database, the indexes that we create in a table are stored as separate relations. They consume extra space. For example, if an index is created on an attribute X of relation R, then X will consists of at least two columns, one for index attribute and the other for pointer.
  • Indexes slows-down the data queries that try to INSERT, DELETE or UPDATE data in the database - The records (keys) in indexes are stored in sorted order. This property helps in speeding up the look-up process. So, whenever we perform INSERT, DELETE, or UPDATE operation on the base table, the records in index has to be adjusted. This slows-down the process.

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