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<h2 id="viewdef"><a href="rbafzmst02.htm#ToC_35">Views</a></h2><a id="idx102" name="idx102"></a>
<p>A <span class="italic">view</span> provides an alternative way of looking at
the data in one or more tables.</p>
<p>A view is a named specification of a result table. The specification is
a SELECT statement that is effectively executed whenever the view is referenced
in an SQL statement. Thus, a view can be thought of as having columns and
rows just like a base table. For retrieval, all views can be used just like
base tables. Whether a view can be used in an insert, update, or delete operation
depends on its definition.</p>
<p>An index cannot be created for a view. However, an index created for a
table on which a view is based may improve the performance of operations on
the view.</p>
<p>When the column of a view is directly derived from a column of a base table,
that column inherits any constraints that apply to the column of the base
table. For example, if a view includes a foreign key of its base table, INSERT
and UPDATE operations using that view are subject to the same referential
constraints as the base table. Likewise, if the base table of a view is a
parent table, DELETE operations using that view are subject to the same rules
as DELETE operations on the base table. A view also inherits any triggers
that apply to its base table. For example, if the base table of a view has
an update trigger, the trigger is fired when an update is performed on the
view.</p>
<p>A view has a name and may have a different system name. The system name
is the name used by i5/OS. Either name is acceptable wherever a <span class="italic">view-name</span> is specified in SQL statements.</p><a id="idx103" name="idx103"></a>
<p>A column of a view has a name and may have a different system column name.
The system column name is the name used by i5/OS. Either name is acceptable
wherever <span class="italic">column-name</span> is specified in SQL statements.</p>
<p>A <span class="italic">view</span> is created with the CREATE VIEW statement.
For more information about creating views, see <a href="rbafzmsthcview.htm#hcview">CREATE VIEW</a>.</p>
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