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- A view is actually a composition of a table in the form of a predefined SQL query.
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- A view can contain all rows of a table or select rows from a table.
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- A view can be created from one or many tables which depends on the written SQL query to create a view.
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- Views, which are a type of virtual tables allow users to do the following −
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-
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Views, which are a type of virtual tables allow users to do the following −
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**- Structure data in a way that users or classes of users find natural or intuitive.**
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@@ -813,4 +814,24 @@ The following guidelines indicate when the use of an index should be reconsidere
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## Updating a View
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-
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A view can be updated under certain conditions which are given below −
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**- The SELECT clause may not contain the keyword DISTINCT.
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The SELECT clause may not contain summary functions.
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The SELECT clause may not contain set functions.
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The SELECT clause may not contain set operators.
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The SELECT clause may not contain an ORDER BY clause.
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The FROM clause may not contain multiple tables.
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The WHERE clause may not contain subqueries.
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The query may not contain GROUP BY or HAVING.
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Calculated columns may not be updated.
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All NOT NULL columns from the base table must be included in the view in order for the INSERT query to function.
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