July 2010
Intermediate to advanced
840 pages
16h 33m
English
Content preview from Joe Celko's SQL for Smarties, 3rd Edition
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6.1. Empty and Missing Tables
An empty table or view is a different concept from a missing table. An empty table is one that is defined with columns and constraints, but that has zero rows in it. This can happen when a table or view is created for the first time, or when all the rows are deleted from the table. It is a perfectly good table. By definition, all of its constraints are TRUE.
A missing table has been removed from the database schema with a DROP TABLE statement, or it never existed at all (you probably typed the name wrong). A missing view is a bit different. It, too, can be absent because of a DROP VIEW statement or a typing error. But it can also be absent because a table or view from which it was built has been removed. This means ...
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