Order entries by category field

Question

I'm loading a set of entries related to 'category' and ordering them by the value of a Dropdown field in the entries. This work well using this code:

{% set entries = craft.entries.relatedTo(category).order('myDropdownField') %}

Now I need to change the Dropdown field to a Category field, but I am not able to sort my entries by this new category field by swapping the dropdown with the category field like this:

{% set entries = craft.entries.relatedTo(category).order('myNewCatField') %}

It gives me this error:

CDbCommand failed to execute the SQL statement: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'departmentCat' in 'order clause'.

I also tried to use the Craft group filter, but I could not make it work in my setting.

Any suggestions are appreciated!

Answer 1

Here's a solution using the group filter.

{% set entriesGrouped = craft.entries.relatedTo(category).order('title')|group('myNewCategoriesField.first().title') %}

{% for group in entriesGrouped %}
    {% for entry in group %}

        {# ... #}

    {% endfor %}
{% endfor %}

Answer 2

As far as I'm aware, you can only order by columns in the content table. Relationships (like categories) are stored in a separate table, and are returned as arrays (or array-like objects in the case of ElementCriteriaModels) and thus not really possible to sort on.

What you may need to do is use both 'category' and 'departmentCat' in the ElementCriteriaModel.

{% set departmentCategories = craft.categories.group('departmentCat') %}
{% for departmentCategory in departmentCategories %}
    {% set entries = craft.entries.relatedTo(
        'and', 
        { targetElement: category }, 
        { targetElement: departmentCategory }
    ).orderBy('title) %}
    {% for entry in entries %}
        {{ entry.title }}
    {% endfor %}
{% endfor %}