Updated the observer/read query to increase performance.
Updated the observer/read query to increase performance.

The observer/read query has been split into sub-queries which is increasing performance by reduing the overhead of temporary tables used by MySQL.

Closes #440

HaiJiaoXinHeng/server-1,hongsudt/server,HaiJiaoXinHeng/server-1,hongsudt/server,hongsudt/server,HaiJiaoXinHeng/server-1