FOR ALL ENTRIES is used to replace nested select loops by
operations on internal tables.

Things to be considerd when working with 'for all entries':

1)Make sure that the select contains atleast the primary key
fields

2)IF NOT <ITAB> IS INITIAL. is a mandatory check before FOR
ALL ENTRIES.

Prerequisites for "FOR ALL ENTRIES"
-----------------------------------
1) Check the higher level internal table having the data or
not. i.e (for eg)
 IF not IT_EKKO is inital.
  
2)sort that internal table

3)delete the adjacent duplicates

4)consider all posssible key combinations in the WHERE condition