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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="create_database">
<title>CREATE DATABASE Statement</title>
<titlealts audience="PDF"><navtitle>CREATE DATABASE</navtitle></titlealts>
<data name="Category" value="Impala"/>
<data name="Category" value="SQL"/>
<data name="Category" value="Databases"/>
<data name="Category" value="Schemas"/>
<data name="Category" value="DDL"/>
<data name="Category" value="S3"/>
<data name="Category" value="Developers"/>
<data name="Category" value="Data Analysts"/>
<indexterm audience="hidden">CREATE DATABASE statement</indexterm>
Creates a new database.
In Impala, a database is both:
A logical construct for grouping together related tables, views, and functions within their own namespace.
You might use a separate database for each application, set of related tables, or round of experimentation.
A physical construct represented by a directory tree in HDFS. Tables (internal tables), partitions, and
data files are all located under this directory. You can perform HDFS-level operations such as backing it up and measuring space usage,
or remove it with a <codeph>DROP DATABASE</codeph> statement.
<p conref="../shared/impala_common.xml#common/syntax_blurb"/>
<codeblock>CREATE (DATABASE|SCHEMA) [IF NOT EXISTS] <varname>database_name</varname>[COMMENT '<varname>database_comment</varname>']
[LOCATION <varname>hdfs_path</varname>];</codeblock>
<p conref="../shared/impala_common.xml#common/ddl_blurb"/>
<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
A database is physically represented as a directory in HDFS, with a filename extension <codeph>.db</codeph>,
under the main Impala data directory. If the associated HDFS directory does not exist, it is created for you.
All databases and their associated directories are top-level objects, with no physical or logical nesting.
After creating a database, to make it the current database within an <cmdname>impala-shell</cmdname> session,
use the <codeph>USE</codeph> statement. You can refer to tables in the current database without prepending
any qualifier to their names.
When you first connect to Impala through <cmdname>impala-shell</cmdname>, the database you start in (before
issuing any <codeph>CREATE DATABASE</codeph> or <codeph>USE</codeph> statements) is named
<p conref="../shared/impala_common.xml#common/builtins_db"/>
After creating a database, your <cmdname>impala-shell</cmdname> session or another
<cmdname>impala-shell</cmdname> connected to the same node can immediately access that database. To access
the database through the Impala daemon on a different node, issue the <codeph>INVALIDATE METADATA</codeph>
statement first while connected to that other node.
Setting the <codeph>LOCATION</codeph> attribute for a new database is a way to work with sets of files in an
HDFS directory structure outside the default Impala data directory, as opposed to setting the
<codeph>LOCATION</codeph> attribute for each individual table.
<p conref="../shared/impala_common.xml#common/sync_ddl_blurb"/>
<p conref="../shared/impala_common.xml#common/hive_blurb"/>
When you create a database in Impala, the database can also be used by Hive.
When you create a database in Hive, issue an <codeph>INVALIDATE METADATA</codeph>
statement in Impala to make Impala permanently aware of the new database.
The <codeph>SHOW DATABASES</codeph> statement lists all databases, or the databases whose name
matches a wildcard pattern. <ph rev="2.5.0">In <keyword keyref="impala25_full"/> and higher, the
<codeph>SHOW DATABASES</codeph> output includes a second column that displays the associated
comment, if any, for each database.</ph>
<p conref="../shared/impala_common.xml#common/s3_blurb"/>
<p rev="2.6.0 IMPALA-1878">
To specify that any tables created within a database reside on the Amazon S3 system,
you can include an <codeph>s3a://</codeph> prefix on the <codeph>LOCATION</codeph>
attribute. In <keyword keyref="impala26_full"/> and higher, Impala automatically creates any
required folders as the databases, tables, and partitions are created, and removes
them when they are dropped.
<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 parent HDFS directory under which the database
is located.
<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"/>
<xref href="impala_databases.xml#databases"/>, <xref href="impala_drop_database.xml#drop_database"/>,
<xref href="impala_use.xml#use"/>, <xref href="impala_show.xml#show_databases"/>,
<xref href="impala_tables.xml#tables"/>