RelatedTo Query Using Both "and" and "or"

Question

I'm attempting to build a filter that queries entries of a section based on two criteria: A selection of one or more categories (inclusive), and a single related entry (exclusive).

Specifically, the entries are from the "technologies" section. Each technology is related to one or more categories and a single "institution" entry.

The first step is to allow a user to, for example, select two categories (like "Information Technology" and "Medical Devices") and have the results be inclusive. Easily done with a relatedTo "or" parameter.

But next, I'd like the user to be able to select a single institution, and return only the previous results that are also associated with that institution (like "UW-Oshkosh"). This filter requires an additional relatedTo "and" parameter.

My attempt to add two different relatedTo parameters to the same query (detailed below) doesn't fly -- it will only honor the last relatedTo request:

{% set params = {
    section: 'technologies',
    limit: null
} %}

{% if technologyIds|length %}
    {% set paramTechnologyRelation = ['or'] %}
    {% for technologyId in technologyIds %}
        {% set paramTechnologyRelation = paramTechnologyRelation|merge([{ targetElement:technologyId }]) %}
    {% endfor %}
    {% set params = params|merge({relatedTo: paramTechnologyRelation}) %}
{% endif %}

{% if institutionId != "" %}
    {% set paramInstitutionRelation = ['and'] %}
    {% set paramInstitutionRelation = paramInstitutionRelation|merge([{ targetElement:institutionId }]) %}
    {% set params = params|merge({relatedTo: paramInstitutionRelation}) %}
{% endif %}

{% set technologyResults = craft.entries(params) %}

{% paginate technologyResults.limit(10) as technologies %}
    ...
{% endpaginate %}

I'm trying to think of other approaches -- Is is possible to run a second query on an array of entries? Any ideas on how to best approach this? Thanks for any insights.

Answer 1

Crisis averted, thanks largely in part to the versitile nature of the relatedTo targetElement processing. The relevation came that I could feed an array of category ids (inclusive) into that element, and use a single relatedTo "and" parameter overall to get my intended filtering:

{% set params = {
    section: 'technologies',
    limit: null
} %}

{% set paramRelation = ['and'] %}
{% if technologyIds|length %}
    {% set paramRelation = paramRelation|merge([{ targetElement:technologyIds }]) %}
{% endif %}
{% if institutionId != "" %}
    {% set paramRelation = paramRelation|merge([{ targetElement:institutionId }]) %}
{% endif %}
{% if paramRelation|length > 1 %}
    {% set params = params|merge({relatedTo: paramRelation}) %}
{% endif %}

{% set technologyResults = craft.entries(params) %}

{% paginate technologyResults.limit(10) as technologies %}
    ...
{% endpaginate %}

It's actually more simple this way as well, but I had initially underestimated how much heavy lifting the targetElement piece could do. Once again, Craft exceeds expectations. Thanks!