January 2008
Intermediate to advanced
384 pages
8h 1m
English
Content preview from Joe Celko's Thinking in Sets: Auxiliary, Temporal, and Virtual Tables in SQL
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Chapter 6. Views
A VIEW IS a virtual table defined by a query that does not exist until it is invoked by name in an SQL statement. I will get into details about what the invocation can mean in physical terms shortly. The Standard SQL syntax for the VIEW definition is
CREATE VIEW <table name> [(<view column list>)] AS <query expression> [WITH [<levels clause>] CHECK OPTION] <levels clause> ::= CASCADED | LOCAL
The <levels clause> option in the WITH CHECK OPTION did not exist in SQL-89 and it is still not widely implemented. This clause has no effect on queries, but only on UPDATE, INSERT, and DELETE statements. You cannot put constraints on a VIEW, as you can with base and TEMPORARY tables. A VIEW has no existence in the database until it is ...
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