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Oracle Tips by Burleson |
True story
A user wanted to change a rate for one
department. He created and ran his update statement, but he did not
use a WHERE clause to limit the changes to the one department. All
rows where changed. He realized his mistake, knowing that he did not
want to commit the incorrect changes; he instead logged off to go get
the DBA to help him. His log off committed the bad data and the
company had to restore the previous night’s backup and recover the
database forward to a time before the user made his changes.
A rollback is issued whenever a user issues the
rollback command, abnormally exits the database or the database
crashes.
Once a commit has been issued, all changes are
permanent. The previous state of the data is permanently lost. Other
users will see the committed changes.
Once a rollback has been issued, the changes are
undone back to the last commit, rollback or log on. All of the
changes are lost (no roll forward).
The above book excerpt is from:
Easy Oracle
SQL
Get Started
Fast writing SQL Reports with SQL*Plus
ISBN 0-9727513-7-8
Col. John Garmany
http://www.rampant-books.com/book_2005_1_easy_sql.htm |
