.. include:: ../../Includes.txt

.. _usingAndDevelopingQueryManagers:

===================================
Using and Developing Query Managers
===================================

Query managers are used in <query> tags to execute queries which can be used in charts.

SAV Charts extension comes with an internal query manager named **savcharts** which can
deal with TYPO3 database queries as well as queries from other databases.

Using the Query Manager
=======================

In the backend in list mode create a new record in a page or a folder.

.. figure:: ../../Images/Tutorial/InternalQueryManager.png

Select **Database** if you need to access to an external database, 
fill the different fields and save.

.. tip::

   You do not need to create a new database access if you only need 
   to access to the current TYPO3 database.

.. figure:: ../../Images/Tutorial/InternalQueryManagerNewDatabase.png

Select **Query** to create a query. Select a database (default is 
**TYPO3 Database**), fill the different clauses and save. 

The following figure illustrates the query to display the number of pages per year.

.. figure:: ../../Images/Tutorial/InternalQueryManagerNewQuery.png

Assuming that the new query has the id **1**, the following flexform 
configuration displays a bar chart with the 
number of pages per year. 

.. figure:: ../../Images/Tutorial/barChartWithQueryFlexformConfiguration.png

In the **Queries** section, the default query manager **savcharts** is used. 
It calls the query whose uid is 1.

The **Data** section of the flexform overloads the template to display 
only a single barchart
with the data provided by the query, as explained in the section :ref:`usingAdvancedTemplates`.


.. important::

   The flag **Allow queries (Admin)** must be set by an Admin user in the content 
   flexform to execute queries.

Go to the frontend to display the resulting chart.

.. figure:: ../../Images/Tutorial/barChartWithQueryInFrontEnd.png

Developing Your Query Manager
=============================

Query managers are implemented by means of hooks.The hook for the internal query manager 
is in **Classes/Hooks/SavChartsQueryManager.php**. This class extends the abstract class 
AbstractQueryManager (**Classes/Hooks/AbstractQueryManager.php**)
which itself implements the interface QueryManagerInterface 
(**Classes/Hooks/QueryManagerInterface.php**).

You can develop your own query manager by providing a hook which must 
be added in the file **ext_localconf.php**
of your extension. 

Assuming that your vendor name is **MyVendorName** and your extension 
name is **my_extension**. Assuming also 
that you have written your manager as the class MyQueryManager 
in **Classes/Hooks/MyQueryManager.php**. 
Finally, assuming that you want to name your query manager **myManager**, you should add 
the following code in **ext_localconf.php** of your extension.

.. code::

   $TYPO3_CONF_VARS['EXTCONF'][$_EXTKEY]['queryManagerClass']['myManager'] = \MyVendorName\MyExtension\Hooks\MyQueryManager::class;