topic Re: synthetic key in QlikView

synthetic key

deepakqlikview_123 — Fri, 23 May 2014 05:20:05 GMT

Is synthetic keys gives faulty result.

Thanks

Re: synthetic key

anbu1984 — Fri, 23 May 2014 05:59:37 GMT

Re: synthetic key

tresB — Fri, 23 May 2014 06:03:55 GMT

Read this, one of the best threads in this community: Should We Stop Worrying and Love the Synthetic Key?

Re: synthetic key

hic — Fri, 23 May 2014 06:46:51 GMT

No, synthetic keys are not bad - not in themselves. And they don't give faulty results.

But if you have an incorrect data model, you will end up with many synthetic keys. And faulty results. But the faulty results are a result of the incorrect data model, not of the synthetic keys.

Read this

http://community.qlik.com/blogs/qlikviewdesignblog/2013/04/16/synthetic-keys

HIC

Re: synthetic key

SunilChauhan — Fri, 23 May 2014 06:49:24 GMT

yes in some cases

one syn key may not impact data

fo example: when you use intervalmatch it left with one syn key

hope this helps

Re: synthetic key

its_anandrjs — Fri, 23 May 2014 07:42:37 GMT

Absolutely No it will help you for your data model but if there are many synthetic keys then there are many synthetic tables then they will occur problem for your data model. When you reload your data model it will slow because the synthetic table is maintain in the data model also if your data model is not perfect like primary key or foreign key concept of the SQL is not meet the perfect result may also effect your data model.

But synthetic keys help you to identify the key reference among the multiple tables.

Regards

Re: synthetic key

SunilChauhan — Fri, 23 May 2014 10:16:56 GMT

Hi Anand,

I agree with your points.

but if see the link below and please t me provide your view on syn key

hope this helps to understand the impact of syn key

http://community.qlik.com/thread/10279?start=30&tstart=0

Re: synthetic key

SunilChauhan — Fri, 23 May 2014 10:37:41 GMT

one more question if they are not impacting then why qliktech recommend to remove them.

i thing synthetic key may lead to poor data model and poor data model may lead to poor results also.

plase correct me if i am wrong somewhere

Re: synthetic key

hic — Fri, 23 May 2014 10:42:33 GMT

My view - and my answer to John's thread - can be read here:

http://community.qlik.com/blogs/qlikviewdesignblog/2013/04/16/synthetic-keys

John writes that he believes that the problems are caused by bad data models, not by the synthetic keys in themselves, and concludes by "Who has an actual problem CAUSED by synthetic keys, rather than by an underlying data model problem?"

I absolutely agree with John. And I have been working in the core team of the QlikView development for twenty years... I was there when we (QlikTech R&D) introduced the synthetic keys.

The bottom line is that Synthetic keys are good! But if you have a bad data model where QlikView creates synthetic keys based on other synthetic keys, then QlikView eats memory and your application is unusable. And the solution is to fix your data model.

HIC

Re: synthetic key

its_anandrjs — Fri, 23 May 2014 10:49:32 GMT

From my point of view, Yes it is right that to remove them and i also agree with Henric. If there is lot of synthetic keys and more synthetic tables are created then need to remove them. Because it affects the data model also if data model is not proper then my cause bad effect to the data model. Also if there is less tables then synthetic keys are much helper and easier to find the relationship between table and keys for large data model where many tables and huge data will be give performance issue to you.

And you could find that there is more keys are present which has relation between the tables by synthetic tables they will help you for this.

They are helpful to find if two or many same keys are present in the tables then they created the synthetic keys, then bu synthetic keys or table we identified that the keys are present in more then tables.

See more information about synthetic keys on community.

Thanks & Regards

Anand

Re: synthetic key

SunilChauhan — Fri, 23 May 2014 11:01:54 GMT

@ henric ,

thanks for your reply's

I afraid with word "Synthetic keys are good"but remaining part is ok for me. i have seen many places syn key are bad. its bit confusing.

@Anand: what is the meaning of it

Also if there is less tables them synthetic keys are much helper and easier to find the relation and between table and keys.

could you please elaborate more where Syn key are much helper and easier to find relation.

i have never seen syn key helper its may cause problems.

it better provide some examples.

i appreciat your responses.

Thanks

Sunil

Re: synthetic key

hic — Fri, 23 May 2014 11:13:13 GMT

Well, I still claim that synthetic keys are good - in principle. If you have a data model where two tables should be linked with two keys (See here for instance) a synthetic key is usually the bar far best solution.

The problem is only (also for me) that when you get synthetic keys in your application, it is usually not because you wanted them, but because you made a mistake in your data model.

HIC

Re: synthetic key

SunilChauhan — Fri, 23 May 2014 15:02:23 GMT

Thanks henric ,I respect your reply. infact it was helpful to me

Thanks to anand also

Thanks you both