sql server - transfer data from one database to another regarding keys -

how can transfer rows 2 tables (patient , contactdetails) db1 db2? both dbs, have these 2 tables data. want add data these 2 tables db1 db2.

i tried following that

but didnt work, because there rows same keys , overwrite forbidden.

is there other way it? or missing something?

patient , contactdetails relationship is

patient inner join contactdetails (foreign_key)patient.contactdetailsid = (primary_key)contactdetails.id 

loop on source contactdetails table, insert each row 1 time saving in temp table old contactdetail id , matching new contactdetail id (here example of sql loop).
temp table should like:

create @temptableforcopy table (  oldcontactdetailsid [insertheretherightdatatype],  newcontactdetailsid [insertheretherightdatatype] ) 

copy data patient table joined temp table used previous step this:

insert newdb.newschema.patient (contactdetailsid, field1, field2, ...) select tt.newcontactdetailsid,        old.field1,        old.field2,        ...   olddb.oldschema.patient old        join @temptableforcopy tt on tt.oldcontactdetailsid = old.contactdetailsid 

please note proposal wild guess: gave no information structure, keys, constraints, no detail key preventing copy error message, solution discarded, amount of data have deal with...