Search Null and a particular value in Solr

Question

I have a column COUNTRY AS

<field name="COUNTRY" type="string" indexed="true" stored="true">

I need to search value of country as usa or blank value but I am not able to do it.

I have tried

fq=country[ U]

fq=country['' U]

fq=country[NULL U]

but nothing has worked.

Answer 1

Based on the answers to these previous questions

• How to OR null value in Apache Solr query?
• Searching for date range or null/no field in Solr

You should be able to use one of the following:

 -(-(country:usa)+(country:{* TO *})) 

 (-country:[* TO *] AND *:*) OR country:usa