Concatenate or Link Table

[#1]

Dear All,

I have many tables and having similar data in many table...Which creates synthetic key and circular loops..

I know we can use Concatenate and Link Table for solving this...

But can anyone tell me the tell me the advantage and disadvantages of using Linktable & Concatenate.

Please be some specific point when to use link table instead of concatenated or vise versa...

Rahul

[richard_pearce6]

Concatenation would be the normal way to create a large fact table (with dimensions as a star schema).

Sometimes that doesn't work. For instance I worked on a project which had two main data sources. One was telephone data and the other was system entries. So a call came in, was handled and things were typed into a customer account....

The two things were linked but not by the data. The only thing loosly linking the two events were the time and who answered the call.

A link table joined the two fact tables on all known dimension conbinations. You turn the dimensions in each fact into a composite key and that plus the original dimensions are moved to the link table. This is repeated for all fact tables you're wishing to join.

The resulting link table is now very long all though very thin so its not too bad for memory,

Richard

[ashfaq_haseeb]

Hi,

Check this post.

http://community.qlik.com/blogs/qlikviewdesignblog/2013/05/17/concatenate-vs-link-table

Regards

ASHFAQ

[Anonymous]

Hi,

given your description (many tables with similiar data) you should concatenate these in one Fact table, this is the easiest way.  for a discussion of if link table or not more information about data would be helpful.

Best regards

Stefan

[#5]

Thank Richard for discussing there problem with me...

@Stefan sorry for the lines(many tables with similar data)...Actually I am asking about where to use Link table instead of concatenation ....And please correct me if i am wrong..I understand that I'll go for Link table if i working on 2 or more database and they are having same fields which creates synthetic key and circular loops....

so mainly its occurs when we work on different type of sources or any other main reasons ..??

rahul