what's wrong with this ?

You need to unlearn the syntax of the language you are used to. You create a variable and assign a value in Appian just using "=" ":" not ":=".

And, Appian uses a functional language paradigm where variables are immutable. So your foreach will also not work.

and one more thing stefan can you please guide me here

I want my result to be in a single list {a,b,c,d,e,f} but I am getting result as  {{a,b}, {c,d}, {e,f}}

You can try using a!flatten.

You try to load all data into memory. That will not work. Appian has some low and hard limits on resource allocation. What are you trying to achieve?

And to learn the basics of Appian, I highly recommend the Appian academy, tutorials and documentation. And I am running a blog and podcast on https://appian.rocks.

You try to load all data into memory. That will not work. Appian has some low and hard limits on resource allocation. What are you trying to achieve?

And to learn the basics of Appian, I highly recommend the Appian academy, tutorials and documentation. And I am running a blog and podcast on https://appian.rocks.

I have mentioned it earlier as well that I want to compare data from appian report and the data present in database, I know you have mentioned about the procedure also but that's not possible as I need those unique details further as well which makes my solution more complicate and here I am fetching the data in batches and then using it , now is that also a problem in appian ?

Depending on the data volume, this will get you in trouble. So I need to repeat my suggestion from the other thread: Write the data to a DB table and run a stored procedure.

considering there is a purging also scheduled.. may I know how much volume it can handle properly without any trouble so I can schedule the purging accordingly.. 

docs.appian.com/.../Memory_Circuit_Breaker.html