Atomicity & Aggregation in Database Management System

Replies

• 

  PraveenKumar Purushothaman

  Atomicity - An atom cannot be subdivided further. So should be the transaction.
  Consider a bank transfer account. In that, A transfers 10 to B. So, database'ically',
  Operation #1: 10 is subtracted from A.
  Operation #2: 10 is added to B.
  Atomicity is both these two operations should happen or none should happen. It cannot be only Operation #1 happened or Operation #2 happened. 😀 Both the operations happened is called a Transaction. 😀
• 

  PraveenKumar Purushothaman

  Aggregation: There are 7 functions in aggregation in databases. All these can be performed only on multiple rows / data.

  AVG()   - Returns the average value
  COUNT() - Returns the number of rows
  FIRST() - Returns the first value
  LAST()  - Returns the last value
  MAX()   - Returns the largest value
  MIN()   - Returns the smallest value
  SUM()   - Returns the sum