Dear Ahmed,
as mentioned you have to define the data source "User Search" so that you only get one user account.
Please see the following configuration which should clarify the case. In this test case (I assume it's similar than your configuration) I have defined one ERP system and LDAP as data sources.
"User Data Search Configuration"
CED_M_9 is my test ERP system and gathering data from SU01.
LDAP_S is my LDAP connection to get data from active directory.
If I know search for a user, lets say last name "Banzer" I will find BANZER_A from ERP and ABA from active directory (LDAP). See as follows:
If you only want to have 1 record found you have either to remove LDAP or ERP from data source. If both sources are defined as user search user will be found in both systems (if exist).
Hope this helps.
Regards,
Alessandro