We have requirement to join 3 tables and fetch the datas. But 2 tables are present in External DB and one table is present in Pega DB. Is it possible to join external and Pega DB tables in Connect-SQL to write a query.
It's nothing that I've tried before. But I can't see how it would be able to run the query unless you have some kind of DBLink between the two databases.
Even then they would need to be issued as a single db user (I believe).
Otherwise if you only have the option to perform this as two separate queries you may want run two Connect-SQL rules (or one for the external data and standard Pega techniques such as obj-browse) to collect data from the two sources, then merge them in the application code.