JQL for issues whitout child issues

[PEGE]

How can I find issues in my project that have no child issues yet?

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I have 3 seperate projects. Project A,B and C.

Project A contains the parent issues for the issues in project B. Project B contains the parent issues for the issues in project C.

I would like to find the issues in project B that have no children in project A. How can I find those issues in project B?

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I've been struggeling with JQL's like 

project = parentproject and (project = childproject and issueFunction not in hasLinkType("Parent-Child Link"))

but that gives no results.

That that query comes up with no results is quite understandable because I'm basicly looking for child issues with no parent (because JQL searches with the parent link are looking up to parent projects) but these child issues do'nt exist.

[Benjamin]

Hi @PEGE ,

Welcome. 

How are you linking the issues between projects? Do you have a specific link type you are using?

Usually, you'll need a third party app in this case to enhance the JQL search.

Please view this post as this is similar to what you are trying to achieve.

https://community.atlassian.com/forums/Jira-questions/JQL-query-for-linked-issues-in-a-specific-project/qaq-p/2808620