topic Re: use of hash() function in QlikView

use of hash() function

pradeep92 — Wed, 25 Nov 2020 16:16:04 GMT

I know hash() function can be used to make fields of variable length to fixed length but when is the situation to use it ?

Re: use of hash() function

Miguel_Angel_Baeyens — Tue, 31 Oct 2017 14:36:58 GMT

In the same situations than AutoNumber(), when you want to uniquely identify the same string across the application but using a fixed length string instead of a variable one (i.e.: street names or full names).

Also when you have a composite key (i.e. concatenating several values from different fields) you have created using several fields to uniquely identify a row in the data model by a smaller/fixed length value.

I never saw the case to use the Hash*() functions, but always the AutoNumber() function instead.

Re: use of hash() function

pradeep92 — Wed, 01 Nov 2017 07:21:24 GMT

Then as of my understanding, autonumber() and hash () function are the same in giving unique values but autonumber() return integer whereas hash() returns string.. Is this right ?

Re: use of hash() function

Miguel_Angel_Baeyens — Wed, 01 Nov 2017 07:52:18 GMT

AutoNumber() function just generates a sequential, integer number for each possible distinct value in the parameter, based on such value.
Hash*() functions do calculate a hash, and return that hash as a literal (string).
AutoNumberHash*() functions do both: first calculate the hash, then take that hash as a parameter and return an integer, sequential number based on it.

Re: use of hash() function

JaMajka1 — Mon, 11 Jun 2018 10:38:46 GMT

Hi Pradeep,

actually hash() always returns the same output for the same input. It does not depend on your data in app and their order as it is in case of autonumber(). So you should use autonumber() only in one final app. If you need to generate the same key across applications (for example multi-layer generators) you should use hash().

BR,

Maria

Re: use of hash() function

pradeep92 — Thu, 28 Jun 2018 05:19:15 GMT

Okay great! thank you