MySQL Proxy on Current User I'm trying to grant permissions to the current user logged in depending on their role, but it doesn't seem possible to have a select statement at the end of the GRANT PROXY # TO # command

The code I have for this is 

CASE (SELECT RoleType FROM user)
WHEN 'standard' THEN
    GRANT PROXY ON 'standard_user'@'localhost' TO (SELECT CURRENT_USER())
WHEN 'admin' THEN
    GRANT PROXY ON 'admin_user'@'localhost' TO (SELECT 'Username' FROM user)@'%'
END CASE;


Does anyone have another idea on how I can achieve this?
I found the answer to be,

CASE (SELECT RoleType FROM user)
    WHEN 'standard' THEN
        GRANT PROXY ON 'standard_user'@'localhost' TO CURRENT_USER();
    WHEN 'admin' THEN
        GRANT PROXY ON 'admin_user'@'localhost' TO CURRENT_USER();
END CASE;