A picture says more then a thousand words:
If you want an overview of the Employee’s skill grouped by skillcategory, then drop a datagrid on your page, select as datasource: database for entity EmployeeSkill. You can add as searchfield via righclick ‘Add attribute’ → other the name of the skillcategory:
Define four entities: Employee, EmployeeSkill, Skill, SkillCategory. EmployeeSkill contains skill category and references Employee and Skill; Skill references SkillCategory. If you need to flatten these tables into a single data grid, base your grid on EmployeeSkill and references the other attributes from related entities.
This model is not Mendix specific. You would design like this using any other platform.
Thank you very much Miroslav and Tim.
My model already matched your suggestions and using Category.Name in a search field did the trick.
But I had to use the Employee’s relation instead of database to restrict the data to the Employee’s skills.
One remaining question:
What would be to do, to not use a search button/tool bar and instead triggering the search directly by the drop down?