Concat data without circular loop

[mohan2391]

hi,

i have 4 tables connected with each other like below

table - fields

---------------------

table1 - key1, f1

table2 - key1, key2

table3 - key2,key3

table4 - key3, f4

now i want a new field with the name NEW_FIELD with the data from f1 and f2 fields

Ex: f1 has values a,b,c

      f2 has values d,e,f

      then NEW_FIELD should have data as a,b,c,d,e,f

how should i achieve this without syn.keys/circular loops ?