1) Source dbscript.sql
2) Add report to enabled_modules in apps/orangehrm/config/settings.yml
3) ./symfony doctrine:build-model
4) ./symfony orangehrm:publish-assets
5) ./symfony cc

Adding report menu:

Add the code given below in index.php to add a report menu..

/* Start Report menu */
$menuItem = new MenuItem("report", "Advanced Reports", './symfony/web/index.php/report/displayAllReports', "rightMenu");
$menu[] = $menuItem;

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Valid join definitions :

Case 1 :

<join>
    <join_by sub_report="mainTable" id="empNumber"></join_by>
    <join_by sub_report="subTable1" id="empNumber"></join_by>
    <join_by sub_report="subTable2" id="empNumber"></join_by>
// You can join any number of tables here assuming that all of them has a common field to join
</join>

Case 2 :
<join as="result1">
    <join_by sub_report="mainTable" id="empNumber"></join_by>
    <join_by sub_report="subTable1" id="empNumber"></join_by>   
</join>
<join as="result2">
    <join_by sub_report="result1" id="coun_code"></join_by>
    <join_by sub_report="subTable2" id="coun_code"></join_by>
</join>
<join>
    <join_by sub_report="result2" id="reg_num"></join_by>
    <join_by sub_report="subTable3" id="reg_num"></join_by>
</join>