Sometimes we want to find issues, where company has or hasn't other issues. For example, at Teamlead we have projects Deals. There we track Deals (issues). And we have another project - Hosting, where we track hosting Instances (issues). So, we want to see Instances, which have no any Deals in status Delivery to control payments etc.
To resolve this requirement we'v add special JQL operator into CRM:
Let's have a look at full example of JQL: