docs/build/plain-html/topics/impala_databases.html - impala - Git at Google

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   <h1 class="title topictitle1" id="ariaid-title1">Overview of Impala Databases</h1>


   <div class="body conbody">

     <p class="p">
       In Impala, a database is a logical container for a group of tables. Each database defines a separate
       namespace. Within a database, you can refer to the tables inside it using their unqualified names. Different
       databases can contain tables with identical names.
     </p>


     <p class="p"> Creating a database is a lightweight operation. There are minimal
       database-specific properties to configure, such as
         <code class="ph codeph">LOCATION</code> and <code class="ph codeph">COMMENT</code>. </p>

     <p class="p">You can change the owner of a database with the <code class="ph codeph">ALTER
         DATABASE</code> statement. </p>


     <p class="p">
       Typically, you create a separate database for each project or application, to avoid naming conflicts between
       tables and to make clear which tables are related to each other. The <code class="ph codeph">USE</code> statement lets
       you switch between databases. Unqualified references to tables, views, and functions refer to objects
       within the current database. You can also refer to objects in other databases by using qualified names
       of the form <code class="ph codeph"><var class="keyword varname">dbname</var>.<var class="keyword varname">object_name</var></code>.
     </p>


     <p class="p">
       Each database is physically represented by a directory in HDFS. When you do not specify a <code class="ph codeph">LOCATION</code>
       attribute, the directory is located in the Impala data directory with the associated tables managed by Impala.
       When you do specify a <code class="ph codeph">LOCATION</code> attribute, any read and write operations for tables in that
       database are relative to the specified HDFS directory.
     </p>


     <p class="p">
       There is a special database, named <code class="ph codeph">default</code>, where you begin when you connect to Impala.
       Tables created in <code class="ph codeph">default</code> are physically located one level higher in HDFS than all the
       user-created databases.
     </p>


     <div class="p">
         Impala includes another predefined database, <code class="ph codeph">_impala_builtins</code>, that
         serves as the location for the
         <a class="xref" href="../shared/../topics/impala_functions.html#builtins">built-in functions</a>. To see
         the built-in functions, use a statement like the following:
 <pre class="pre codeblock"><code>show functions in _impala_builtins;
 show functions in _impala_builtins like '*<var class="keyword varname">substring</var>*';
 </code></pre>
       </div>


     <p class="p">
       <strong class="ph b">Related statements:</strong>
     </p>


     <p class="p">
       <a class="xref" href="impala_create_database.html#create_database">CREATE DATABASE Statement</a>,
       <a class="xref" href="impala_drop_database.html#drop_database">DROP DATABASE Statement</a>, <a class="xref" href="impala_use.html#use">USE Statement</a>,
       <a class="xref" href="impala_show.html#show_databases">SHOW DATABASES</a>
     </p>

   </div>

 <div class="related-links">
 <div class="familylinks">
 <div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_schema_objects.html">Impala Schema Objects and Object Names</a></div>
 </div>
 </div></body>
 </html>
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	<head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

	<meta name="copyright" content="(C) Copyright 2025" />
	<meta name="DC.rights.owner" content="(C) Copyright 2025" />
	<meta name="DC.Type" content="concept" />
	<meta name="DC.Title" content="Overview of Impala Databases" />
	<meta name="DC.Relation" scheme="URI" content="../topics/impala_schema_objects.html" />
	<meta name="prodname" content="Impala" />
	<meta name="prodname" content="Impala" />
	<meta name="version" content="Impala 3.4.x" />
	<meta name="version" content="Impala 3.4.x" />
	<meta name="DC.Format" content="XHTML" />
	<meta name="DC.Identifier" content="databases" />
	<link rel="stylesheet" type="text/css" href="../commonltr.css" />
	<title>Overview of Impala Databases</title>
	</head>
	<body id="databases">


	<h1 class="title topictitle1" id="ariaid-title1">Overview of Impala Databases</h1>




	<div class="body conbody">

	<p class="p">
	In Impala, a database is a logical container for a group of tables. Each database defines a separate
	namespace. Within a database, you can refer to the tables inside it using their unqualified names. Different
	databases can contain tables with identical names.
	</p>


	<p class="p"> Creating a database is a lightweight operation. There are minimal
	database-specific properties to configure, such as
	<code class="ph codeph">LOCATION</code> and <code class="ph codeph">COMMENT</code>. </p>

	<p class="p">You can change the owner of a database with the <code class="ph codeph">ALTER
	DATABASE</code> statement. </p>


	<p class="p">
	Typically, you create a separate database for each project or application, to avoid naming conflicts between
	tables and to make clear which tables are related to each other. The <code class="ph codeph">USE</code> statement lets
	you switch between databases. Unqualified references to tables, views, and functions refer to objects
	within the current database. You can also refer to objects in other databases by using qualified names
	of the form <code class="ph codeph"><var class="keyword varname">dbname</var>.<var class="keyword varname">object_name</var></code>.
	</p>


	<p class="p">
	Each database is physically represented by a directory in HDFS. When you do not specify a <code class="ph codeph">LOCATION</code>
	attribute, the directory is located in the Impala data directory with the associated tables managed by Impala.
	When you do specify a <code class="ph codeph">LOCATION</code> attribute, any read and write operations for tables in that
	database are relative to the specified HDFS directory.
	</p>


	<p class="p">
	There is a special database, named <code class="ph codeph">default</code>, where you begin when you connect to Impala.
	Tables created in <code class="ph codeph">default</code> are physically located one level higher in HDFS than all the
	user-created databases.
	</p>


	<div class="p">
	Impala includes another predefined database, <code class="ph codeph">_impala_builtins</code>, that
	serves as the location for the
	<a class="xref" href="../shared/../topics/impala_functions.html#builtins">built-in functions</a>. To see
	the built-in functions, use a statement like the following:
	<pre class="pre codeblock"><code>show functions in _impala_builtins;
	show functions in _impala_builtins like '<var class="keyword varname">substring</var>';
	</code></pre>
	</div>


	<p class="p">
	<strong class="ph b">Related statements:</strong>
	</p>


	<p class="p">
	<a class="xref" href="impala_create_database.html#create_database">CREATE DATABASE Statement</a>,
	<a class="xref" href="impala_drop_database.html#drop_database">DROP DATABASE Statement</a>, <a class="xref" href="impala_use.html#use">USE Statement</a>,
	<a class="xref" href="impala_show.html#show_databases">SHOW DATABASES</a>
	</p>

	</div>

	<div class="related-links">
	<div class="familylinks">
	<div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_schema_objects.html">Impala Schema Objects and Object Names</a></div>
	</div>
	</div></body>
	</html>