impala/docs/topics/impala_drop_database.xml

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

  <title>DROP DATABASE Statement</title>
  <titlealts audience="PDF"><navtitle>DROP DATABASE</navtitle></titlealts>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Databases"/>
      <data name="Category" value="DDL"/>
      <data name="Category" value="Schemas"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      <indexterm audience="hidden">DROP DATABASE statement</indexterm>
      Removes a database from the system. The physical operations involve removing the metadata for the database
      from the metastore, and deleting the corresponding <codeph>*.db</codeph> directory from HDFS.
    </p>

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

<codeblock>DROP (DATABASE|SCHEMA) [IF EXISTS] <varname>database_name</varname> <ph rev="2.3.0">[RESTRICT | CASCADE]</ph>;</codeblock>

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

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

    <p>
      By default, the database must be empty before it can be dropped, to avoid losing any data.
    </p>

    <p rev="2.3.0">
      In <keyword keyref="impala23_full"/> and higher, you can include the <codeph>CASCADE</codeph>
      clause to make Impala drop all tables and other objects in the database before dropping the database itself.
      The <codeph>RESTRICT</codeph> clause enforces the original requirement that the database be empty
      before being dropped. Because the <codeph>RESTRICT</codeph> behavior is still the default, this
      clause is optional.
    </p>

    <p rev="2.3.0">
      The automatic dropping resulting from the <codeph>CASCADE</codeph> clause follows the same rules as the
      corresponding <codeph>DROP TABLE</codeph>, <codeph>DROP VIEW</codeph>, and <codeph>DROP FUNCTION</codeph> statements.
      In particular, the HDFS directories and data files for any external tables are left behind when the
      tables are removed.
    </p>

    <p>
      When you do not use the <codeph>CASCADE</codeph> clause, drop or move all the objects inside the database manually
      before dropping the database itself:
    </p>

    <ul>
      <li>
        <p>
          Use the <codeph>SHOW TABLES</codeph> statement to locate all tables and views in the database,
          and issue <codeph>DROP TABLE</codeph> and <codeph>DROP VIEW</codeph> statements to remove them all.
        </p>
      </li>
      <li>
        <p>
          Use the <codeph>SHOW FUNCTIONS</codeph> and <codeph>SHOW AGGREGATE FUNCTIONS</codeph> statements
          to locate all user-defined functions in the database, and issue <codeph>DROP FUNCTION</codeph>
          and <codeph>DROP AGGREGATE FUNCTION</codeph> statements to remove them all.
        </p>
      </li>
      <li>
        <p>
          To keep tables or views contained by a database while removing the database itself, use
          <codeph>ALTER TABLE</codeph> and <codeph>ALTER VIEW</codeph> to move the relevant
          objects to a different database before dropping the original database.
        </p>
      </li>
    </ul>

    <p>
      You cannot drop the current database, that is, the database your session connected to
      either through the <codeph>USE</codeph> statement or the <codeph>-d</codeph> option of <cmdname>impala-shell</cmdname>.
      Issue a <codeph>USE</codeph> statement to switch to a different database first.
      Because the <codeph>default</codeph> database is always available, issuing
      <codeph>USE default</codeph> is a convenient way to leave the current database
      before dropping it.
    </p>

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

    <p>
      When you drop a database in Impala, the database can no longer be used by Hive.
    </p>

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

<!-- Better to conref the same examples in both places. -->

    <p>
      See <xref href="impala_create_database.xml#create_database"/> for examples covering <codeph>CREATE
      DATABASE</codeph>, <codeph>USE</codeph>, and <codeph>DROP DATABASE</codeph>.
    </p>

    <p conref="../shared/impala_common.xml#common/s3_blurb"/>

    <p conref="../shared/impala_common.xml#common/s3_ddl"/>

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

    <p conref="../shared/impala_common.xml#common/permissions_blurb"/>
    <p rev="">
      The user ID that the <cmdname>impalad</cmdname> daemon runs under,
      typically the <codeph>impala</codeph> user, must have write
      permission for the directory associated with the database.
    </p>

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

    <codeblock conref="../shared/impala_common.xml#common/create_drop_db_example"/>

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

    <p>
      <xref href="impala_databases.xml#databases"/>, <xref href="impala_create_database.xml#create_database"/>,
      <xref href="impala_use.xml#use"/>, <xref href="impala_show.xml#show_databases"/>, <xref href="impala_drop_table.xml#drop_table"/>
    </p>
  </conbody>
</concept>