SQL & PL/SQL

Hi All,

I am trying to understand the following SQL statement written in the code I am reading but could not make out how to divide it into seperate pieces to understand what is happening at which stage.

This is the query

select TO_CHAR(FROM_TZ(CAST(TO_DATE(fsh.start_time, 'DD/MM/YY') AS
                            TIMESTAMP),
                       'Europe/London') AT TIME ZONE 'Asia/Singapore',
               'hh24:mi:ss')
  from feed_status_history fsh

I am told that it converts the ''Europe/London' time zone to 'Asia/Singapore' zone but I am not able to make out how is it taking place. The actual problem is that I am not understanding what this "AT TIME ZONE" thing does ?

Please help me to understand the meaning of this query and how it might be working for FROM_TZ, CAST etc.

Thanks,
Aashish