title: Exclude fields with null values in SOLR queries
body: <p>I am trying to make a url request to an API that uses SOLR for queries.</p>
  
  <p>I have a lot of data with a lot of fields that contains different values and often some of those fields will contain a null value.</p>
  
  <p>I want to make a query where I retrieve all the data where specific fields are not null, but contain some actual value.</p>
  
  <p>For example each entry contains a field called tags which is an array of tags. a tag could for example be the word test.</p>
  
  <p>I have tried doing -tags:[* TO *] and that results in all the data sets where tags is null to be returned.</p>
  
  <p>I have also tried tags:[* TO *] that returns all data, both where tags are null and where tags are actually set.</p>
  
  <p>I have been trying all sorts of things to get to the last case, where only tags with values are returned and I hope you can help me?</p>