ogr__api_8h.html

gdal库的学习文档

  </table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>NULL is returned on failure, or a new <a class="el" href="classOGRLayer.html">OGRLayer</a> handle on success.</dd></dl>
<b>Example:</b><p>
<div class="fragment"><pre class="fragment"><span class="preprocessor">#include "<a class="code" href="ogrsf__frmts_8h.html">ogrsf_frmts.h</a>"</span> 
<span class="preprocessor">#include "<a class="code" href="cpl__string_8h.html">cpl_string.h</a>"</span>

...

        OGRLayerH *hLayer;
        <span class="keywordtype">char</span>     *papszOptions;

        <span class="keywordflow">if</span>( <a class="code" href="ogr__api_8h.html#d0fefab726442fa71ab5ef74fe8549a6">OGR_DS_TestCapability</a>( hDS, ODsCreateLayer ) )
        {
            ...
        }

        papszOptions = CSLSetNameValue( papszOptions, <span class="stringliteral">"DIM"</span>, <span class="stringliteral">"2"</span> );
        hLayer = <a class="code" href="ogr__api_8h.html#424d383a37fbeaea58acaea11717f320">OGR_DS_CreateLayer</a>( hDS, <span class="stringliteral">"NewLayer"</span>, NULL, wkbUnknown,
                                     papszOptions );
        CSLDestroy( papszOptions );

        <span class="keywordflow">if</span>( hLayer == NULL )
        {
            ...
        }        
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<a class="anchor" name="9892ecb0bf61add295bd9decdb13797a"></a><!-- doxytag: member="ogr_api.h::OGR_DS_ExecuteSQL" ref="9892ecb0bf61add295bd9decdb13797a" args="(OGRDataSourceH, const char *, OGRGeometryH, const char *)" -->
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          <td class="memname">OGRLayerH OGR_DS_ExecuteSQL           </td>
          <td>(</td>
          <td class="paramtype">OGRDataSourceH&nbsp;</td>
          <td class="paramname"> <em>hDS</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">const char *&nbsp;</td>
          <td class="paramname"> <em>pszSQLCommand</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">OGRGeometryH&nbsp;</td>
          <td class="paramname"> <em>hSpatialFilter</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">const char *&nbsp;</td>
          <td class="paramname"> <em>pszDialect</em></td><td>&nbsp;</td>
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<p>
Execute an SQL statement against the data store.<p>
The result of an SQL query is either NULL for statements that are in error, or that have no results set, or an <a class="el" href="classOGRLayer.html">OGRLayer</a> handle representing a results set from the query. Note that this <a class="el" href="classOGRLayer.html">OGRLayer</a> is in addition to the layers in the data store and must be destroyed with OGR_DS_ReleaseResultsSet() before the data source is closed (destroyed).<p>
For more information on the SQL dialect supported internally by OGR review the <a href="ogr_sql.html">OGR SQL</a> document. Some drivers (ie. Oracle and PostGIS) pass the SQL directly through to the underlying RDBMS.<p>
This function is the same as the C++ method <a class="el" href="classOGRDataSource.html#a6acc228db6513784a56ce12334a8c33">OGRDataSource::ExecuteSQL()</a>;<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign="top"></td><td valign="top"><em>hDS</em>&nbsp;</td><td>handle to the data source on which the SQL query is executed. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>pszSQLCommand</em>&nbsp;</td><td>the SQL statement to execute. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>hSpatialFilter</em>&nbsp;</td><td>handle to a geometry which represents a spatial filter. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>pszDialect</em>&nbsp;</td><td>allows control of the statement dialect. By default it is assumed to be "generic" SQL, whatever that is.</td></tr>
  </table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>an handle to a <a class="el" href="classOGRLayer.html">OGRLayer</a> containing the results of the query. Deallocate with OGR_DS_ReleaseResultsSet(). </dd></dl>

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<a class="anchor" name="03998029f904d1c3b12de40114e7503e"></a><!-- doxytag: member="ogr_api.h::OGR_DS_GetLayer" ref="03998029f904d1c3b12de40114e7503e" args="(OGRDataSourceH, int)" -->
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          <td class="memname">OGRLayerH OGR_DS_GetLayer           </td>
          <td>(</td>
          <td class="paramtype">OGRDataSourceH&nbsp;</td>
          <td class="paramname"> <em>hDS</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">int&nbsp;</td>
          <td class="paramname"> <em>iLayer</em></td><td>&nbsp;</td>
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          <td>)</td>
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<p>
Fetch a layer by index. The returned layer remains owned by the <a class="el" href="classOGRDataSource.html">OGRDataSource</a> and should not be deleted by the application.<p>
This function is the same as the C++ method <a class="el" href="classOGRDataSource.html#618c2fdb1067c9357ca2de9fa6cd5962">OGRDataSource::GetLayer()</a>.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign="top"></td><td valign="top"><em>hDS</em>&nbsp;</td><td>handle to the data source from which to get the layer. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>iLayer</em>&nbsp;</td><td>a layer number between 0 and <a class="el" href="ogr__api_8h.html#c6da541cb655ab631df729e71da2e762">OGR_DS_GetLayerCount()</a>-1.</td></tr>
  </table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>an handle to the layer, or NULL if iLayer is out of range or an error occurs. </dd></dl>

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<a class="anchor" name="74af4912b67bf2a7b6e3230711a40d0e"></a><!-- doxytag: member="ogr_api.h::OGR_DS_GetLayerByName" ref="74af4912b67bf2a7b6e3230711a40d0e" args="(OGRDataSourceH, const char *)" -->
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          <td class="memname">OGRLayerH OGR_DS_GetLayerByName           </td>
          <td>(</td>
          <td class="paramtype">OGRDataSourceH&nbsp;</td>
          <td class="paramname"> <em>hDS</em>, </td>
        </tr>
        <tr>
          <td class="paramkey"></td>
          <td></td>
          <td class="paramtype">const char *&nbsp;</td>
          <td class="paramname"> <em>pszLayerName</em></td><td>&nbsp;</td>
        </tr>
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          <td></td>
          <td>)</td>
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<p>
Fetch a layer by name. The returned layer remains owned by the <a class="el" href="classOGRDataSource.html">OGRDataSource</a> and should not be deleted by the application.<p>
This function is the same as the C++ method <a class="el" href="classOGRDataSource.html#a0fafafc83084ad140ecdf17d9e139f9">OGRDataSource::GetLayerByName()</a>.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign="top"></td><td valign="top"><em>hDS</em>&nbsp;</td><td>handle to the data source from which to get the layer. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>psz</em>&nbsp;</td><td>Layer the layer name of the layer to fetch.</td></tr>
  </table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>an handle to the layer, or NULL if the layer is not found or an error occurs. </dd></dl>

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<a class="anchor" name="c6da541cb655ab631df729e71da2e762"></a><!-- doxytag: member="ogr_api.h::OGR_DS_GetLayerCount" ref="c6da541cb655ab631df729e71da2e762" args="(OGRDataSourceH)" -->
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          <td class="memname">int OGR_DS_GetLayerCount           </td>
          <td>(</td>
          <td class="paramtype">OGRDataSourceH&nbsp;</td>
          <td class="paramname"> <em>hDS</em>          </td>
          <td>&nbsp;)&nbsp;</td>
          <td width="100%"></td>
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<p>