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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="use">
<title>USE Statement</title>
<titlealts audience="PDF"><navtitle>USE</navtitle></titlealts>
<data name="Category" value="Impala"/>
<data name="Category" value="SQL"/>
<data name="Category" value="Databases"/>
<data name="Category" value="Developers"/>
<data name="Category" value="Data Analysts"/>
<indexterm audience="hidden">USE statement</indexterm>
Switches the current session to a specified database. The <term>current database</term> is where any
<codeph>CREATE TABLE</codeph>, <codeph>INSERT</codeph>, <codeph>SELECT</codeph>, or other statements act when
you specify a table or other object name, without prefixing it with a database name. The new current database
applies for the duration of the session or unti another <codeph>USE</codeph> statement is executed.
<p conref="../shared/impala_common.xml#common/syntax_blurb"/>
<codeblock>USE <varname>db_name</varname></codeblock>
By default, when you connect to an Impala instance, you begin in a database named <codeph>default</codeph>.
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
Switching the default database is convenient in the following situations:
To avoid qualifying each reference to a table with the database name. For example, <codeph>SELECT * FROM t1
JOIN t2</codeph> rather than <codeph>SELECT * FROM db.t1 JOIN db.t2</codeph>.
To do a sequence of operations all within the same database, such as creating a table, inserting data, and
querying the table.
To start the <cmdname>impala-shell</cmdname> interpreter and automatically issue a <codeph>USE</codeph>
statement for a particular database, specify the option <codeph>-d <varname>db_name</varname></codeph> for
the <cmdname>impala-shell</cmdname> command. The <codeph>-d</codeph> option is useful to run SQL scripts,
such as setup or test scripts, against multiple databases without hardcoding a <codeph>USE</codeph> statement
into the SQL source.
<p conref="../shared/impala_common.xml#common/example_blurb"/>
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 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/related_info"/>
<xref href="impala_create_database.xml#create_database"/>,
<xref href="impala_drop_database.xml#drop_database"/>, <xref href="impala_show.xml#show_databases"/>