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| <h1 class="title topictitle1" id="ariaid-title1">COMMENT Statement</h1> |
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| <p class="p"> |
| The <code class="ph codeph">COMMENT</code> statement adds, changes, or removes a comment about a |
| database, a table, or a column. |
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| <p class="p"> |
| You can alternatively use the <code class="ph codeph">CREATE</code> and <code class="ph codeph">ALTER</code> |
| statements to add comments to the objects. |
| </p> |
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| <p class="p"> |
| You can view the comment on a database, a table, or a column using the |
| <code class="ph codeph">SHOW</code> or <code class="ph codeph">DESCRIBE</code> statement. |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Syntax:</strong> |
| </p> |
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| <pre class="pre codeblock"><code>COMMENT ON DATABASE <var class="keyword varname">db_name</var> IS {'<var class="keyword varname">comment</var>' | NULL}</code></pre> |
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| <pre class="pre codeblock"><code>COMMENT ON TABLE [<var class="keyword varname">db_name</var>.]<var class="keyword varname">table_name</var> IS {'<var class="keyword varname">comment</var>' | NULL}</code></pre> |
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| <pre class="pre codeblock"><code>COMMENT ON COLUMN [<var class="keyword varname">db_name</var>.]<var class="keyword varname">table_name</var>.<var class="keyword varname">column_name</var> IS {'<var class="keyword varname">comment</var>' | NULL}</code></pre> |
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| <strong class="ph b">Parameters:</strong> |
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| <li class="li"> |
| <var class="keyword varname">db_name</var>: Specify the database name if not for the current database. |
| </li> |
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| <li class="li"> |
| <code class="ph codeph">NULL</code>: If given for the comment, removes the existing comment. |
| </li> |
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| <li class="li"> |
| The <var class="keyword varname">comment</var> string can be up to 256 characters long. |
| </li> |
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| </ul> |
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| <p class="p"> |
| <strong class="ph b">Privileges required:</strong> |
| </p> |
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| <p class="p"> |
| To add a comment, the <code class="ph codeph">ALTER</code> privilege on the object is required. |
| </p> |
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| <p class="p"> |
| To view a comment, the <code class="ph codeph">SELECT</code>, <code class="ph codeph">INSERT</code>, or |
| <code class="ph codeph">REFRESH</code> on the object is required. |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Usage notes:</strong> |
| </p> |
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| <p class="p"> |
| <strong class="ph b">Added in:</strong> <span class="keyword">Impala 3.1</span> |
| </p> |
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| </div> |
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| <div class="related-links"> |
| <div class="familylinks"> |
| <div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_langref_sql.html">Impala SQL Statements</a></div> |
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