When do we use Link tables in QV ?

[Anonymous]

Hi,

Why and When do we use Link tables in QV data modeling . How is it different from Concatenation or joining the tables .

Thank you !

[oknotsen]

You use a Link table when the facts do not share all the same dimensions.

[tresesco]

This blog :Concatenate vs Link Table should be helpful.

[gautik92]

if there are more than one fact table we create link table

[sujeetsingh]

A table which links between two tables having relationship One to Many.

[oknotsen]

That would mean you have a link table between almost every table.

I think you are mistaking "link table" for "link".

[Anonymous]

Hi,

Please go through following links,

what is use of link tables ,how to use it

link table

What is Link Tables? What is the use?

thanks,

bunny

[Anonymous]

Hi Mamtha,

In Data warehousing - Star schema usually have a single Fact in the centre and dimensions surrounding it but sometimes you have a situation where you have more than one Fact table.

In Qlikview,You come across a situation where you have to handle multiple Fact tables, which in turn create synthetic keys.

Link Table is a very useful way to resolve synthetic keys when multiple fact tables are present in the data model.

Link table is used, when the granularity of the facts tables are different and when they are joined to different dimensions.

To resolve these synthetic keys Link table:

• You should always load Distinct records while creating Link table. Also if the Key field/composite field contains several individual fields then it is good to create Key field
• Create a composite key. Using Auto number ( ) function like:
• AutoNumber(YEAR&’|'&CUSTOMER_KEY&’|'&PRODUCT_KEY) As [%Key field]
• Link table can connect to the original fact tables using this composite Key
• Load all the common fields in one table called Link table
• Drop these fields from the original tables.

[Anonymous]

Thank you Neetha !