docs/topics/impala_alter_view.xml

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept rev="1.1" id="alter_view">

  <title>ALTER VIEW Statement</title>
  <titlealts audience="PDF"><navtitle>ALTER VIEW</navtitle></titlealts>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="DDL"/>
      <data name="Category" value="Tables"/>
      <data name="Category" value="Schemas"/>
      <data name="Category" value="Views"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      <indexterm audience="hidden">ALTER VIEW statement</indexterm>
      Changes the characteristics of a view. The syntax has two forms:
    </p>

    <ul>
      <li>
        The <codeph>AS</codeph> clause associates the view with a different query.
      </li>
      <li>
        The <codeph>RENAME TO</codeph> clause changes the name of the view, moves the view to
        a different database, or both.
      </li>
    </ul>

    <p>
      Because a view is purely a logical construct (an alias for a query) with no physical data behind it,
      <codeph>ALTER VIEW</codeph> only involves changes to metadata in the metastore database, not any data files
      in HDFS.
    </p>

<!-- View _permissions_ don't rely on underlying table. -->

<!-- Could use views to grant access only to certain columns. -->

<!-- Treated like a table for authorization. -->

<!-- ALTER VIEW that queries another view - possibly a runtime error. -->

    <p conref="../shared/impala_common.xml#common/syntax_blurb"/>

<codeblock>ALTER VIEW [<varname>database_name</varname>.]<varname>view_name</varname> AS <varname>select_statement</varname>
ALTER VIEW [<varname>database_name</varname>.]<varname>view_name</varname> RENAME TO [<varname>database_name</varname>.]<varname>view_name</varname></codeblock>

    <p conref="../shared/impala_common.xml#common/ddl_blurb"/>

    <p conref="../shared/impala_common.xml#common/sync_ddl_blurb"/>

    <p conref="../shared/impala_common.xml#common/security_blurb"/>
    <p conref="../shared/impala_common.xml#common/redaction_yes"/>

    <p conref="../shared/impala_common.xml#common/cancel_blurb_no"/>

    <p conref="../shared/impala_common.xml#common/permissions_blurb_no"/>

    <p conref="../shared/impala_common.xml#common/example_blurb"/>

<codeblock>create table t1 (x int, y int, s string);
create table t2 like t1;
create view v1 as select * from t1;
alter view v1 as select * from t2;
alter view v1 as select x, upper(s) s from t2;</codeblock>

<!-- Repeat the same blurb + example to see the definition of a view, as in CREATE VIEW. -->

    <p conref="../shared/impala_common.xml#common/describe_formatted_view"/>

    <p conref="../shared/impala_common.xml#common/related_info"/>

    <p>
      <xref href="impala_views.xml#views"/>, <xref href="impala_create_view.xml#create_view"/>,
      <xref href="impala_drop_view.xml#drop_view"/>
    </p>
  </conbody>
</concept>