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d484d2f684
This now gives a clean RAT check with bin/check-rat-report.py, which is one way for the Impala community to check compliance with ASF rules on intellectual property. Change-Id: I2ad06435f84a65ba126759e42a18fdaf52cd7036 Reviewed-on: http://gerrit.cloudera.org:8080/5232 Reviewed-by: Jim Apple <jbapple-impala@apache.org> Tested-by: Impala Public Jenkins Reviewed-by: John Russell <jrussell@cloudera.com>
98 lines
3.8 KiB
XML
98 lines
3.8 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="use">
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<title>USE Statement</title>
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<titlealts audience="PDF"><navtitle>USE</navtitle></titlealts>
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<prolog>
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<metadata>
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<data name="Category" value="Impala"/>
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<data name="Category" value="SQL"/>
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<data name="Category" value="Databases"/>
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<data name="Category" value="Developers"/>
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<data name="Category" value="Data Analysts"/>
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</metadata>
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</prolog>
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<conbody>
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<p>
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<indexterm audience="Cloudera">USE statement</indexterm>
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Switches the current session to a specified database. The <term>current database</term> is where any
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<codeph>CREATE TABLE</codeph>, <codeph>INSERT</codeph>, <codeph>SELECT</codeph>, or other statements act when
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you specify a table or other object name, without prefixing it with a database name. The new current database
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applies for the duration of the session or unti another <codeph>USE</codeph> statement is executed.
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</p>
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<p conref="../shared/impala_common.xml#common/syntax_blurb"/>
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<codeblock>USE <varname>db_name</varname></codeblock>
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<p>
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By default, when you connect to an Impala instance, you begin in a database named <codeph>default</codeph>.
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</p>
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<p conref="../shared/impala_common.xml#common/usage_notes_blurb"/>
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<p>
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Switching the default database is convenient in the following situations:
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</p>
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<ul>
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<li>
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To avoid qualifying each reference to a table with the database name. For example, <codeph>SELECT * FROM t1
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JOIN t2</codeph> rather than <codeph>SELECT * FROM db.t1 JOIN db.t2</codeph>.
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</li>
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<li>
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To do a sequence of operations all within the same database, such as creating a table, inserting data, and
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querying the table.
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</li>
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</ul>
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<p>
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To start the <cmdname>impala-shell</cmdname> interpreter and automatically issue a <codeph>USE</codeph>
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statement for a particular database, specify the option <codeph>-d <varname>db_name</varname></codeph> for
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the <cmdname>impala-shell</cmdname> command. The <codeph>-d</codeph> option is useful to run SQL scripts,
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such as setup or test scripts, against multiple databases without hardcoding a <codeph>USE</codeph> statement
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into the SQL source.
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</p>
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<p conref="../shared/impala_common.xml#common/example_blurb"/>
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<p>
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See <xref href="impala_create_database.xml#create_database"/> for examples covering <codeph>CREATE
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DATABASE</codeph>, <codeph>USE</codeph>, and <codeph>DROP DATABASE</codeph>.
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</p>
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<p conref="../shared/impala_common.xml#common/cancel_blurb_no"/>
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<p conref="../shared/impala_common.xml#common/permissions_blurb_no"/>
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<p conref="../shared/impala_common.xml#common/related_info"/>
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<p>
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<xref href="impala_create_database.xml#create_database"/>,
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<xref href="impala_drop_database.xml#drop_database"/>, <xref href="impala_show.xml#show_databases"/>
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</p>
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</conbody>
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</concept>
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