next up previous
Next: Insertions Up: Modifying the Database Previous: Modifying the Database


  1. Deletion is expressed in much the same way as a query. Instead of displaying, the selected tuples are removed from the database. We can only delete whole tuples.

    In relational algebra, a deletion is of the form

    where is a relation and is a relational algebra query.

    Tuples in for which is true are deleted.

  2. Some examples:

    1. Delete all of Smith's account records.

    2. Delete all loans with loan numbers between 1300 and 1500.

    3. Delete all accounts at Branches located in Needham.

Page created and maintained by Osmar R. Zaï ane
Last Update: Wed Sep 20 15:45:57 PDT 1995