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<title>31.18.key_column_usage</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="infoschema-key-column-usage"></a>31.18.<code class="literal">key_column_usage</code></h2></div></div></div>
<p> The view <code class="literal">key_column_usage</code> identifies all columns
in the current database that are restricted by some unique, primary
key, or foreign key constraint. Check constraints are not included
in this view. Only those columns are shown that are contained in a
table owned by the current user.
</p>
<div class="table">
<a name="id696821"></a><p class="title"><b>Table31.16.<code class="literal">key_column_usage</code> Columns</b></p>
<div class="table-contents"><table summary="key_column_usage Columns" border="1">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Data Type</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td><code class="literal">constraint_catalog</code></td>
<td><code class="type">sql_identifier</code></td>
<td>Name of the database that contains the constraint (always the current database)</td>
</tr>
<tr>
<td><code class="literal">constraint_schema</code></td>
<td><code class="type">sql_identifier</code></td>
<td>Name of the schema that contains the constraint</td>
</tr>
<tr>
<td><code class="literal">constraint_name</code></td>
<td><code class="type">sql_identifier</code></td>
<td>Name of the constraint</td>
</tr>
<tr>
<td><code class="literal">table_catalog</code></td>
<td><code class="type">sql_identifier</code></td>
<td> Name of the database that contains the table that contains the
column that is restricted by some constraint (always the
current database)
</td>
</tr>
<tr>
<td><code class="literal">table_schema</code></td>
<td><code class="type">sql_identifier</code></td>
<td> Name of the schema that contains the table that contains the
column that is restricted by some constraint
</td>
</tr>
<tr>
<td><code class="literal">table_name</code></td>
<td><code class="type">sql_identifier</code></td>
<td> Name of the table that contains the column that is restricted
by some constraint
</td>
</tr>
<tr>
<td><code class="literal">column_name</code></td>
<td><code class="type">sql_identifier</code></td>
<td> Name of the column that is restricted by some constraint
</td>
</tr>
<tr>
<td><code class="literal">ordinal_position</code></td>
<td><code class="type">cardinal_number</code></td>
<td> Ordinal position of the column within the constraint key (count
starts at 1)
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break">
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