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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> pointer 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 OGRDataSource::ReleaseResultsSet() before the data source is closed (destroyed).<p>
This method is the same as the C function <a class="el" href="ogr__api_8h.html#9892ecb0bf61add295bd9decdb13797a">OGR_DS_ExecuteSQL()</a>.<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>
<dl compact><dt><b>Parameters:</b></dt><dd>
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    <tr><td valign="top"></td><td valign="top"><em>pszStatement</em>&nbsp;</td><td>the SQL statement to execute. </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>poSpatialFilter</em>&nbsp;</td><td>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>
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<dl class="return" compact><dt><b>Returns:</b></dt><dd>an <a class="el" href="classOGRLayer.html">OGRLayer</a> containing the results of the query. Deallocate with ReleaseResultsSet(). </dd></dl>

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<a class="anchor" name="7d3ee7601f510a87afc76de8a51aa9b1"></a><!-- doxytag: member="OGRDataSource::ReleaseResultSet" ref="7d3ee7601f510a87afc76de8a51aa9b1" args="(OGRLayer *poResultsSet)" -->
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Release results of <a class="el" href="classOGRDataSource.html#a6acc228db6513784a56ce12334a8c33">ExecuteSQL()</a>.<p>
This method should only be used to deallocate OGRLayers resulting from an <a class="el" href="classOGRDataSource.html#a6acc228db6513784a56ce12334a8c33">ExecuteSQL()</a> call on the same <a class="el" href="classOGRDataSource.html">OGRDataSource</a>. Failure to deallocate a results set before destroying the <a class="el" href="classOGRDataSource.html">OGRDataSource</a> may cause errors.<p>
This method is the same as the C function OGR_L_ReleaseResultsSet().<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
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    <tr><td valign="top"></td><td valign="top"><em>poResultsSet</em>&nbsp;</td><td>the result of a previous <a class="el" href="classOGRDataSource.html#a6acc228db6513784a56ce12334a8c33">ExecuteSQL()</a> call. </td></tr>
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<a class="anchor" name="1af1c7cf202f9a2ca2310bbfa3d00cca"></a><!-- doxytag: member="OGRDataSource::SyncToDisk" ref="1af1c7cf202f9a2ca2310bbfa3d00cca" args="()" -->
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Flush pending changes to disk.<p>
This call is intended to force the datasource to flush any pending writes to disk, and leave the disk file in a consistent state. It would not normally have any effect on read-only datasources.<p>
Some data sources do not implement this method, and will still return OGRERR_NONE. An error is only returned if an error occurs while attempting to flush to disk.<p>
The default implementation of this method just calls the <a class="el" href="classOGRDataSource.html#1af1c7cf202f9a2ca2310bbfa3d00cca">SyncToDisk()</a> method on each of the layers. Conceptionally, calling <a class="el" href="classOGRDataSource.html#1af1c7cf202f9a2ca2310bbfa3d00cca">SyncToDisk()</a> on a datasource should include any work that might be accomplished by calling <a class="el" href="classOGRDataSource.html#1af1c7cf202f9a2ca2310bbfa3d00cca">SyncToDisk()</a> on layers in that data source.<p>
This method is the same as the C function OGR_DS_SyncToDisk().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>OGRERR_NONE if no error occurs (even if nothing is done) or an error code. </dd></dl>

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<a class="anchor" name="82733127f4498fb4ee1d061d73dd549c"></a><!-- doxytag: member="OGRDataSource::Reference" ref="82733127f4498fb4ee1d061d73dd549c" args="()" -->
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Increment datasource reference count.<p>
This method is the same as the C function OGR_DS_Reference().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>the reference count after incrementing. </dd></dl>

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<a class="anchor" name="538760ac249d06681fd26c383e678cb1"></a><!-- doxytag: member="OGRDataSource::Dereference" ref="538760ac249d06681fd26c383e678cb1" args="()" -->
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Decrement datasource reference count.<p>
This method is the same as the C function OGR_DS_Dereference().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>the reference count after decrementing. </dd></dl>

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<a class="anchor" name="fbfe92dec39e0271a473d4435c692c05"></a><!-- doxytag: member="OGRDataSource::GetRefCount" ref="fbfe92dec39e0271a473d4435c692c05" args="() const" -->
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Fetch reference count.<p>
This method is the same as the C function OGR_DS_GetRefCount().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>the current reference count for the datasource object itself. </dd></dl>

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<a class="anchor" name="a14e7f93d132cd24d120ecf86fb1971e"></a><!-- doxytag: member="OGRDataSource::GetSummaryRefCount" ref="a14e7f93d132cd24d120ecf86fb1971e" args="() const" -->
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Fetch reference count of datasource and all owned layers.<p>
This method is the same as the C function OGR_DS_GetSummaryRefCount().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>the current summary reference count for the datasource and its layers. </dd></dl>

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<a class="anchor" name="e4b1cb2d75f251cfb70d8a9c185a001d"></a><!-- doxytag: member="OGRDataSource::Release" ref="e4b1cb2d75f251cfb70d8a9c185a001d" args="()" -->
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Drop a reference to this datasource, and if the reference count drops to zero close (destroy) the datasource. Internally this actually calls the OGRSFDriverRegistrary::ReleaseDataSource() method. This method is essentially a convenient alias.<p>
This method is the same as the C function OGRReleaseDataSource().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>OGRERR_NONE on success or an error code. </dd></dl>

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<a class="anchor" name="509b66e2ab7fd13e389ca3e633963af8"></a><!-- doxytag: member="OGRDataSource::GetDriver" ref="509b66e2ab7fd13e389ca3e633963af8" args="() const" -->
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          <td class="memname"><a class="el" href="classOGRSFDriver.html">OGRSFDriver</a> * OGRDataSource::GetDriver           </td>
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Returns the driver that the dataset was opened with.<p>
This method is the same as the C function OGR_DS_GetDriver().<p>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>NULL if driver info is not available, or pointer to a driver owned by the OGRSFDriverManager. </dd></dl>

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<hr>The documentation for this class was generated from the following files:<ul>
<li><a class="el" href="ogrsf__frmts_8h-source.html">ogrsf_frmts.h</a><li>ogrsf_frmts.dox<li>ogrdatasource.cpp</ul>
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