Considering the performance factor, the best way to achieve this is
suppose you have table1 and table2 in different indexes or sources or sourcetypes
I am not sure it will work or not but you can always give it a try
index=table1 OR index=table2 | stats dc(index) as dc values(eval(if(index="table2",1,0))) as table2 by TicketNumber | search table2=1 | eval ExistingInTable1?=if(dc=2,"Yes","No") | table TicketNumber ExistingInTable1?
you can choose source or sourcetype instead of index.
let me know if this helps!