topic Re: what is link table plz give with exaple friends. in QlikView

what is link table plz give with exaple friends.

Wed, 09 Sep 2015 19:14:23 GMT

Hi friends this is babu, plz help me this.

what is link table plz give with exaple friends.

plz help me friends.

Re: what is link table plz give with exaple friends.

vikasmahajan — Thu, 10 Sep 2015 05:17:25 GMT

Refer my post explain in details https://community.qlik.com/thread/110627

Vikas

Re: what is link table plz give with exaple friends.

vikasmahajan — Thu, 10 Sep 2015 05:19:18 GMT

also look this Re: what is use of link tables ,how to use it

Re: what is link table plz give with exaple friends.

sujeetsingh — Thu, 10 Sep 2015 05:24:39 GMT

(…) a junction table is a database table that contains common fields from two or more other database tables within the same database. It is on the many side of a one-to-many relationship with each of the other tables. Junction tables are known under many names, among them cross-reference table, bridge table, join table, map table, intersection table, linking table, many-to-many resolver, Link Table, pairing table, pivot table, transition table, or association table. (…).”

Re: what is link table plz give with exaple friends.

gautik92 — Thu, 10 Sep 2015 05:25:53 GMT

If you have two fact tables with some common fields you can concatenate both tables to create a link table.that link table will be like a fact table

Re: what is link table plz give with exaple friends.

prma7799 — Thu, 10 Sep 2015 05:44:01 GMT

Hi Babu,

Please go through below

There are two main strategies to modelling data in QlikView to handle multiple fact tables:

Append your fact tables into one single fact table - usually referred to as a CONCATENATED FACT as QlikView's syntax for appending data to tables is by use of the CONCATENATE prefix (the equivalent of a SQL UNION operation)
Build a link table (what you have done so far) For a majority of implementations, option 1 is the appropriate method. Attributes of a CONCATENATED fact can be summarised as:

Positives:

Performs well due to the reduced number of large tables in the data model
Simple to implement, just append all data to one generic fact table whilst ensuring common dimensions are referenced by common field names

Negatives:

The different facts are NOT directly associated with each other. The implication is important to understand. It means that cross-analysis of facts is typically only achievable by the common dimensions. Any fact specific dimensions do not connect in any way to the records of the facts that do not reference these dimensions. Complex 'set analysis' syntax can to some degree mitigate this shortcoming, but if your core requirement is to do indirect analysis of fact A by fact B's fact specific dimensions then you may need to revert to a link table model instead.

How to construct Link Tables is a complex subject but relies upon traditional database linking table design techniques. It is easy to go wrong and produce linking tables that may seem to produce the correct results in the front-end but is excessively large, consuming memory and CPU resources.

In my experience, a poorly modelled QlikView data model is the most common culprit for causing poor performance.

I hope this quick, far from exhaustive, introduction to multi-fact modelling in QlikView proves of some help and sets you on the right course.

Re: what is link table plz give with exaple friends.

prma7799 — Thu, 10 Sep 2015 05:47:21 GMT

Link tables are generally used for linking the two table or the fact tables. With the use of link tables, it’s possible to keep the fact tables separated from each other. The advantage of this solution for choosing this method is to keep the data model a logical one. With the use of link tables, it’s possible to keep the fact tables separated from each other.

Re: what is link table plz give with exaple friends.

Thu, 10 Sep 2015 06:40:37 GMT

hi,

Go through this link it might help u.

Re: what is use of link tables ,how to use it

Re: what is link table plz give with exaple friends.

Anonymous — Thu, 10 Sep 2015 07:10:51 GMT

HI,

Link tables are what is often outside of QlikView in other BI-environments/DWH and in general called bridge tables. The purpose and the concept is the same. These tables maintain a many-to-many relationship between two or more tables. Link tables should be evaluated in respect to another approach that is CONCATENATED fact tables.

Excerpt from QlikView material about link tables:

When to use a Link Table

Let's look at when a link table might be required. Generally if you have a data model with multiple fact tables, that contain different measures and only minimal common dimensions, then you will likely need a link table. If your fact tables store their data at different levels of granularity i.e. a transactional table with daily data and a targets table with monthly data, then you will almost certainly need a link table. The purpose of the link table is to provide a seamless lik between all data in your application so that QlikView's (or Qlik Sense's) associative technology can be used to it's full potential. A badly implemented Link Table will have a significant and negative impact on the user's experience.

Henric Cronström in several of his blog posts and discussions on this forum recommend using concatenated fact tables in most cases instead of link tables. Link Tables are a necessity however when you need something called an alias dimension or role-playing dimension. Henric Cronström's paper on CANONICAL DATE shows in detail how a link table is created and maintained for this specific purpose

A special case of link table is the automatic creation of synthetic keys which QlikView does in the load script if it encounters two or more tables with more than one field (based on field-name) in common. Then it has to resort to this technique and create an intervening table it calls [$Syn <n> Table]. Also the use of INTERVAL MATCH will create a key and table like that which is in this case absolutely valid and necessary.

Regars

Gireesh

Re: what is link table plz give with exaple friends.

qlikviewwizard — Thu, 10 Sep 2015 08:46:22 GMT

Hi,

Check for link table from slide number 30. Hope this will help you.