In Mysql DBMS is it possible to assign USAGE privileges to a user which can do an update query? In order to prevent SQL-injection.
In mysql usage means that the only facility is to to authenticate the user. Typically a native database account would not be used for authenticating users.
If the user has update privileges (and the application is vulnerable) they can subvert the application.
If you are asking how to provision write-only access for a user, then this can be done by writing directly to the grant tables though this is frowned upon. A more sensible and portable approach is to grant only the exec privilege and use stored procedures with an explicit definer who does have access to the underlying data.