Nested CDTs vs Non Nested CDTs

Question

Hi everyone, 
 I am trying to understand in terms of Appian's best practice as to which way to go when creating CDTs and maintaining their relationships, and the use of nested CDTs. Is it recommended to use nested CDTs per best practice, or is it better to stay away from that? From my understanding, it's easier and better to create the tables in the database first then create CDTs from db where the relationship is maintained strictly in db and not necessarily in Appian. Then there is the other way, in which the cdts are created in Appian, with the relationships maintained through the use of Nested CDTs for the foreign key etc.. Is it a matter of preference to create the CDTs from db vs the other way with nested CDTs, or is it Appian recommended? 
 Any thoughts on this? 
 Regards, 
 Jerry

ravalik · Answer

HI jerrys, 
As far as I know, nested CDTs are not recommended due to several issues like performance degradation , conversion of data becomes difficult and also debugging the process model and accessing the unnecessary data becomes cumbersome.So in order to avoid this you can use plain CDT. 
Refer the link below for more info: 
 community.appian.com/.../database-performance-best-practices.

Thanks, 
ravalik

Shiva Valusa · Answer

Hi, As a best practice it is good to avoid using nested CDT's or maximum one level of nested CDT's are recommended. Please go through following thread around nested CDT's, it may help you. community.appian.com/.../nested-cdts

Farnaz · Answer

Hi Jerry, 
 
As others mentioned, while creating Nested CDT's, we need to check the below mentioned points: 
 
(1) What is the functionality? Can we avoid by proceeding with two or more tables referenced to each other? If not, can we create a complex view having the complete data. I prefer the Complex View. A CDT can be created mapping the complex view can be used in creation of Form(while Storing data), Summary Dashboards (while retrieving data), Records, Reports etc. This is simple and also effects the Performance. 
 
(2) If creating complex View is not feasible, Nested CDT approach can be used. But recommended Best Practice is to have it only for one level. 
 
Thanks, 
Farnaz