# Descriptors Types Recommended / And Unique question

**URL:** <https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224>\
**Category:** Forum\
**Tags:** Adabas-Natural, Adabas, Adabas-Basics-on-Linux-Unix-Windows, Adabas-on-Windows-UNIX, Adabas-on-Linux\
**Created:** [August 15, 2012, 1:28am UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224 "2012-08-15T01:28:18Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![Claudio\_Muller](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/claudio_muller/32/518_2.png) [@Claudio\_Muller](https://techcommunity.softwareag.com/u/Claudio_Muller)\
**Post date:** [August 15, 2012, 1:28am UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/1 "2012-08-15T01:28:18Z")

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which means in practice “unique” for descriptors?

about the various types of descriptors = DE, SB, SP, HY, CO, PH  
I could not find anything that says when each is recommended ?!

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**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\
**Post date:** [August 15, 2012, 1:57am UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/2 "2012-08-15T01:57:05Z")

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Unique means only one inverted list entry will be allowed for any specific descriptor value,  
for example only one record with LastName=“Jones”.

[Introduction to descriptor types](http://techcommunity.softwareag.com/ecosystem/documentation/adabas/ada63os/admin/dbdesign.htm#datacstrat)

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**Author:** ![Claudio\_Muller](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/claudio_muller/32/518_2.png) [@Claudio\_Muller](https://techcommunity.softwareag.com/u/Claudio_Muller)\
**Post date:** [August 15, 2012, 3:06pm UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/3 "2012-08-15T15:06:22Z")

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Thanks. i see.

In windows to create FDT

the field “DDM DC:”

What is this?

I don´t find in documentations.

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<div class="post-metadata">

**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\
**Post date:** [August 15, 2012, 3:28pm UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/4 "2012-08-15T15:28:02Z")

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Why don’t you just click the Help button on the FDT editor window ?

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<div class="post-metadata">

**Author:** ![Claudio\_Muller](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/claudio_muller/32/518_2.png) [@Claudio\_Muller](https://techcommunity.softwareag.com/u/Claudio_Muller)\
**Post date:** [August 15, 2012, 3:43pm UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/5 "2012-08-15T15:43:43Z")

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Sorry

I go to web documentation adabas and i don´t click this option.

I see now.

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<div class="post-metadata">

**Author:** ![Claudio\_Muller](https://sea1.discourse-cdn.com/techcommunity/user_avatar/techcommunity.softwareag.com/claudio_muller/32/518_2.png) [@Claudio\_Muller](https://techcommunity.softwareag.com/u/Claudio_Muller)\
**Post date:** [February 8, 2013, 5:22pm UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/6 "2013-02-08T17:22:07Z")

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The descriptor with Unique Option  
is the same as  
a unique key in other databases like mysql?

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**Author:** ![Matthias1](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@Matthias1](https://techcommunity.softwareag.com/u/Matthias1)\
**Post date:** [February 12, 2013, 8:15am UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/7 "2013-02-12T08:15:08Z")

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> [@Claudio Muller](#):
>
> The descriptor with Unique Option  
> is the same as  
> a unique key in other databases like mysql?

I guess so. When I read [Unique key - Wikipedia](http://en.wikipedia.org/wiki/Unique_key) is sounds like a unique descriptors from an ADABAS point of view (although ADABAS is not a relational database)

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**Author:** ![system](https://global.discourse-cdn.com/techcommunity/original/3X/c/d/cd19967bb605d28a72d77eb83a1cae22f3df2eb8.svg) [@system](https://techcommunity.softwareag.com/u/system)\
**Post date:** [April 2, 2021, 3:02pm UTC](https://techcommunity.softwareag.com/t/descriptors-types-recommended-and-unique-question/101224/8 "2021-04-02T15:02:18Z")

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