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<head><title>Querying </title>
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<h1>Querying</h1>
<p>It is easy
to retrieve all of the Pilot instances from the database: just right-click the
Pilot class in db4o Browser and select "Show All Objects". The list of the
Pilot objects will be shown in the Query Result view:</p>
<p>
<img src="omn_result.jpg" />
</p>
<p>You can see
object details in the detailed view below. Try to change any values and use
Save button to persist the changes to the database. You can also use Delete
button to delete objects from the database. For the objects containing field
objects you will be prompted to use cascade on delete.</p>
<p>More
complex queries can be done by using Query Builder view:</p>
<p>
<img src="omn_query.jpg" />
</p>
<p>Drag "_name"
field from the Db4o Browser view into the Query Builder view, set condition "Contains",
put a value "a" and run the query. You can return to the Built Query tab and
modify the query later on again. For example: add "AND" operator, drag "_name"
field, set Condition to "Starts With" and the value to "M". Re-run the query. </p>
<p>If you want
only selected fields to be displayed in the query result, drag and drop fields
to be displayed from Db4o Browser into "Attribute List" window.</p>
<p>
<img src="omn_attr.jpg" />
</p>
<p>When the
new query is created, the previous query is stored and can be selected from the
history drop-down:</p>
<p>
<img src="omn_qhistory.jpg" />
</p>
<p>More
sophisticated queries can be build by joining grouped constraints using "Add
Group" button.</p>
<p>When you
are done working with the database in <span class="MCTextPopup"><a href="javascript:void(0);" class="MCTextPopupSpot" onclick="FMCTextPopup( event, this ); return false;">OME<img style="border: none;margin-left: 5px;" src="../../SkinSupport/ExpandingClosed.gif" MadCap:altsrc="../../SkinSupport/ExpandingOpen.gif" class="MCExpandingIcon" onload="if ( typeof( FMCPreloadImage ) == 'function' ) { FMCPreloadImage( '../../SkinSupport/ExpandingOpen.gif' ); }" /></a><span class="MCTextPopupBody" style="display: none; ">Object Manager, a tool to view and edit a db4o database</span></span>, you can close the connection by
using Tools->Object Manager Enterprise-> Disconnect menu command or by
using the equivalent button on the toolbar. </p>
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