Question Re: difference between aggregation and projection node in Calculation view in Technology Q&A

difference between aggregation and projection node in Calculation view

Former Member — Tue, 05 Jan 2016 18:30:40 GMT

Hi Please explain the exact difference between aggregation and projection node in Calculation view.I have taken many examples but getting same output, I am not able find out the any difference between these nodes. only difference I can find in aggregation node we have option of "add as aggregated column (min,max..)" but How it works for next level and ""When to use projection"". Please reply with simple example including data. Thanks

Re: difference between aggregation and projection node in Calculation view

former_member200930 — Wed, 06 Jan 2016 00:09:11 GMT

Hi,

I am trying my best to explain difference between projection and aggregation in simple words.

Projection : It is use to select data without aggregation. NO Group By Clause. You will get entire dataset for selected columns.

Aggregation : Group by clause will be used here. So, you will get less number of rows in output.

Example :

I have create calculation view using below dummy table.

Modeling using Projection node :

Output of Projection_1 node :
( After activation, right click on Projection_1 node and select Data Preview. Same is applicable to Aggregation_1 node)

Modeling using Aggregation :

Output of Aggregation_1 node :

Conclusion : Using projection, we got 7 rows and using Aggregation, we got 2 rows. So, Using aggregation you are passing less data to another node. So, execution time will be fast.

Note : You will get same output at semantic layer for Projection and Aggregation.

Regards,

Vikram Divekar

Re: difference between aggregation and projection node in Calculation view

Former Member — Wed, 06 Jan 2016 14:15:08 GMT

Hi,

PROJECTION is only meant for filtering but AGGREGATION is for both filtering and aggregated columns

Best Regards,

Mohammed