I am writing a query that would need user context in query mode. How can I get the Zoho user context in my query. Example

SELECT EMPLOYEE_NAME, EMPLOYEE_ADDRESS FROM EMPLOYEE where 

EMP_USER_NAME = <LOGGED_IN_ZOHO_USER>

How can I get " <LOGGED_IN_ZOHO_USER>" as john@abc.com 

  john@abc.com - is already a registered user in zoho reports.