Questioning regarding Alias Table in Incorta for developers course

[mohamed_kamal]

in Incorta For Developers course, Lab: Schema Workshop, Check#2 and Check#3,
the instructor made an Alias table while the analysis or even the design can be done successfully without making it, as there was no more than one relation between the same two tables.

let's say there's table X and table Y and there's a join relation between both of them, the instructor wanted to introduce a new join relation between table X and table Z, and there was no previous join relation between X and Z. so, Instead of making the relation normally between the two original tables, the instructor made an alias table for X to introduce the new join relation.

so is there another reason that I didn't catch, is there a type of principle in the designing that the instructor follow or what is the point?

Thanks in advance.

[Shashidhar]

Hi kamal,

All joins in Incorta are Left outer joins by default. 

In case 1, the connection is X to Y and Y to Z, and if you want to get data from X and Z, you need to either include the Y object(column) in the query or explicitly reference Y as the driving Table(base). 

But here your secenario from case 2  is a bit different, Y is common parent for both X and Z. If you want to get data from X and Z, then here we need to handle many to many relationship. Here you can take the help of bridge table to solve this. Instead, In developer course, instructor created alias of X and join with Z which you can see in case 3. Sharing few URLs for your reference.

https://community.incorta.com/t5/data-schemas-knowledgebase/modeling-schemas-tables-and-joins/ta-p/7...

https://docs.incorta.com/cloud/concepts-base-table

https://www.youtube.com/watch?v=FJgFiDvToUY

Regards,

Shashidhar.S