I am a new comer in Appian, please help me with steps to implement One to One & One to Many relations.
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There are a number of resources available on this topic -- both via online training and documentation. You might start with "Database Design Basics:" https://academy.appian.com/#/online-courses/62e52c7b-cd92-457a-abd0-98e5f1a81142
Next -- Manage Data Using Custom Data Types: academy.appian.com/, but I recommend this course be taken in sequence through the Appian Developer learning path.
And then for a more advanced, but more in-depth view: https://academy.appian.com/#/online-courses/ce361d9a-79ba-42d0-bc10-a4279d46e874
If you prefer docs -- this is a great article: docs.appian.com/.../CDT_Relationships.html
Manage Data Using Custom Data Types link: https://academy.appian.com/#/online-courses/80d231bb-c1c1-4d4e-8471-d190a6f13070
Kara's suggestions are great - there's a lot of good content on Appian Academy that describes how to use different relationships. I also like this page in the docs on CDT design guidance that describes how to set up different relationship types using CDTs.
I'm also curious - do you have a use case in mind or are you just looking for general guidance? If you have a use case in mind, we can provide a bit more information if you describe your scenario.