Smart QL does not provide a simple column in table ISSUES with issue key. This is because Jira data model does not contain it either. Issue key is a computed field, because it can be changed over time (ie, due to project key changes or moving issue to another project). 

Function takes following parameters:

Examples

SELECT P.KEY || '-' || CAST(I.NUM as VARCHAR) ISSUE_KEY, I.SUMMARY 
FROM ISSUES I 
JOIN PROJECTS P ON I.PROJECT = P.ID
LIMIT 4

SELECT AUX.ASISSUEKEY(I.ID) ISSUE_KEY, I.SUMMARY 
FROM ISSUES I 
LIMIT 4