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doc-exports/docs/dws/dev/dws_06_0343.html
luhuayi 177cd61a57 DWS DEVG 910.211 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: luhuayi <luhuayi@huawei.com>
Co-committed-by: luhuayi <luhuayi@huawei.com>
2025-05-05 07:44:03 +00:00

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<a name="EN-US_TOPIC_0000001811515781"></a><a name="EN-US_TOPIC_0000001811515781"></a>
<h1 class="topictitle1">Comment Checking Functions</h1>
<div id="body0000001503124277"><div class="section" id="EN-US_TOPIC_0000001811515781__section15967181231116"><h4 class="sectiontitle">col_description(table_oid, column_number)</h4><p id="EN-US_TOPIC_0000001811515781__p15967212141117">Description: Gets comment for a table column.</p>
<p id="EN-US_TOPIC_0000001811515781__p196731213111">Return type: text</p>
<p id="EN-US_TOPIC_0000001811515781__p18967131261113">Note: <strong id="EN-US_TOPIC_0000001811515781__b996111390102059">col_description</strong> returns the comment for a table column, which is specified by the OID of its table and its column number.</p>
<p id="EN-US_TOPIC_0000001811515781__p1660015424125">Example: Query the <strong id="EN-US_TOPIC_0000001811515781__b1037517429146">pg_class</strong> system catalog to obtain the table OID, and query the INFORMATION_SCHEMA.COLUMNS system view to obtain <strong id="EN-US_TOPIC_0000001811515781__b1337544216146">column_number</strong>.</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001811515781__screen1212201753616"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="k">COLUMN_NAME</span><span class="p">,</span><span class="n">ORDINAL_POSITION</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">INFORMATION_SCHEMA</span><span class="p">.</span><span class="n">COLUMNS</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="k">TABLE_NAME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">'t'</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="k">COLUMN_NAME</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">'a'</span><span class="p">;</span>
<span class="k">column_name</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ordinal_position</span>
<span class="c1">-------------+------------------</span>
<span class="n">a</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="mi">1</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">oid</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">pg_class</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">relname</span><span class="o">=</span><span class="s1">'t'</span><span class="p">;</span>
<span class="w"> </span><span class="n">oid</span>
<span class="c1">-------</span>
<span class="w"> </span><span class="mi">44020</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
<span class="k">SELECT</span><span class="w"> </span><span class="n">col_description</span><span class="p">(</span><span class="mi">44020</span><span class="p">,</span><span class="mi">1</span><span class="p">);</span>
<span class="w"> </span><span class="n">col_description</span>
<span class="c1">-----------------------</span>
<span class="w"> </span><span class="n">This</span><span class="w"> </span><span class="k">is</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="n">test</span><span class="w"> </span><span class="k">table</span><span class="p">.</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001811515781__section1514171021110"><h4 class="sectiontitle">obj_description(object_oid, catalog_name)</h4><p id="EN-US_TOPIC_0000001811515781__p614111011119">Description: Gets comment for a database object.</p>
<p id="EN-US_TOPIC_0000001811515781__p3141151011114">Return type: text</p>
<p id="EN-US_TOPIC_0000001811515781__p01411910171111">Note: The two-parameter form of <strong id="EN-US_TOPIC_0000001811515781__b1644373676102059">obj_description</strong> returns the comment for a database object specified by its OID and the name of the containing system catalog. For example, <strong id="EN-US_TOPIC_0000001811515781__b739478205102059">obj_description(123456,'pg_class')</strong> would retrieve the comment for the table with OID 123456. The one-parameter form of <strong id="EN-US_TOPIC_0000001811515781__b484045201102059">obj_description</strong> requires only the object OID.</p>
<p id="EN-US_TOPIC_0000001811515781__p914191012111"><strong id="EN-US_TOPIC_0000001811515781__b889677851102059">obj_description</strong> cannot be used for table columns since columns do not have OIDs of their own.</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811515781__section127521904119"><h4 class="sectiontitle">obj_description(object_oid)</h4><p id="EN-US_TOPIC_0000001811515781__p2075217021110">Description: Gets comment for a database object.</p>
<p id="EN-US_TOPIC_0000001811515781__p197526021116">Return type: text</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001811515781__section148283576106"><h4 class="sectiontitle">shobj_description(object_oid, catalog_name)</h4><p id="EN-US_TOPIC_0000001811515781__p19828145781017">Description: Gets comment for a shared database object.</p>
<p id="EN-US_TOPIC_0000001811515781__p148288579104">Return type: text</p>
<p id="EN-US_TOPIC_0000001811515781__p108281657151014">Note: The functions of <strong id="EN-US_TOPIC_0000001811515781__b9703145161518">shobj_description</strong> and <strong id="EN-US_TOPIC_0000001811515781__b36679191516">obj_description</strong> are similar. The only difference is that <strong id="EN-US_TOPIC_0000001811515781__b574214136153">shobj_description</strong> is used for shared objects. Some system catalogs are global to all databases within each cluster, and the comments for objects in them are stored globally as well.</p>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_06_0051.html">System Information Functions</a></div>
</div>
</div>
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