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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="comments">

  <title>Comments</title>
  <prolog>
    <metadata>
      <data name="Category" value="Impala"/>
      <data name="Category" value="SQL"/>
      <data name="Category" value="Developers"/>
      <data name="Category" value="Data Analysts"/>
    </metadata>
  </prolog>

  <conbody>

    <p>
      <indexterm audience="hidden">comments (SQL)</indexterm>
      Impala supports the familiar styles of SQL comments:
    </p>

    <ul>
      <li>
        All text from a <codeph>--</codeph> sequence to the end of the line is considered a comment and ignored.
        This type of comment can occur on a single line by itself, or after all or part of a statement.
      </li>

      <li>
        All text from a <codeph>/*</codeph> sequence to the next <codeph>*/</codeph> sequence is considered a
        comment and ignored. This type of comment can stretch over multiple lines. This type of comment can occur
        on one or more lines by itself, in the middle of a statement, or before or after a statement.
      </li>
    </ul>

    <p>
      For example:
    </p>

<codeblock>-- This line is a comment about a table.
create table ...;

/*
This is a multi-line comment about a query.
*/
select ...;

select * from t /* This is an embedded comment about a query. */ where ...;

select * from t -- This is a trailing comment within a multi-line command.
where ...;
</codeblock>
  </conbody>
</concept>