Tuesday, February 27, 2007

Introduction to Oracle9i: SQL (13)

Creating and managing tables

  • Constraints created on views are not enforced; hence they are called declarative constraints.
  • Row_Num pseudocolumn is used for performing Top-‘N’ analysis.
  • While updating data through a join view only one of the base tables can be updated with one DML statement.
  • Views are masks placed upon tables. Views are used to restrict the access of the user to the data of the base tables they are also referred to as masks on the table.
  • Synonyms are simply a way of accessing table through a shortcut name.
  • Triggers are functions that execute automatically when a specified action takes place on the database.

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