docs/topics/impala_comment.xml

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

  <title>COMMENT Statement</title>

  <titlealts audience="PDF">

    <navtitle>COMMENT</navtitle>

  </titlealts>

  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="DDL"/>
      <data name="Category" value="Tables"/>
      <data name="Category" value="Hive"/>
      <data name="Category" value="Metastore"/>
      <data name="Category" value="ETL"/>
      <data name="Category" value="Ingest"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      The <codeph>COMMENT</codeph> statement adds, changes, or removes a comment about a
      database, a table, or a column.
    </p>

    <p>
      You can alternatively use the <codeph>CREATE</codeph> and <codeph>ALTER</codeph>
      statements to add comments to the objects.
    </p>

    <p>
      You can view the comment on a database, a table, or a column using the
      <codeph>SHOW</codeph> or <codeph>DESCRIBE</codeph> statement.
    </p>

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

<codeblock>COMMENT ON DATABASE <varname>db_name</varname> IS {'<varname>comment</varname>' | NULL}</codeblock>

<codeblock>COMMENT ON TABLE [<varname>db_name</varname>.]<varname>table_name</varname> IS {'<varname>comment</varname>' | NULL}</codeblock>

<codeblock>COMMENT ON COLUMN [<varname>db_name</varname>.]<varname>table_name</varname>.<varname>column_name</varname> IS {'<varname>comment</varname>' | NULL}</codeblock>

    <p>
      <b>Parameters:</b>
    </p>

    <ul>
      <li>
        <varname>db_name</varname>: Specify the database name if not for the current database.
      </li>

      <li>
        <codeph>NULL</codeph>: If given for the comment, removes the existing comment.
      </li>

      <li>
        The <varname>comment</varname> string can be up to 256 characters long.
      </li>
    </ul>

    <p>
      <b>Privileges required:</b>
    </p>

    <p>
      To add a comment, the <codeph>ALTER</codeph> privilege on the object is required.
    </p>

    <p>
      To view a comment, the <codeph>SELECT</codeph>, <codeph>INSERT</codeph>, or
      <codeph>REFRESH</codeph> on the object is required.
    </p>

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

    <p>
      <b>Added in:</b> <keyword keyref="impala31"/>
    </p>

  </conbody>

</concept>