Try following. I am assuming that you have included Title column in your lookup column.
Building a clause for ProjectName="X" and Active="Yes", you have to use $filter operator.
http://<siteurl>/_api/lists/getbytitle('Project%20Locations')/items?$select=Title,ProjectName/Title&$expand=ProjectName&$filter=Active eq 1 and ProjectName/Title eq 'X'
Meaning of the error.
You have to $expand your lookup columns. Target column must be specified in the $select
Regarding $filter by lookup column
- You need to
$expand that column
- In
$select, you have to specify which columns you need to retrieve from lookup column. For example, your lookup list has several columns like Title, Name, EstimatedDate, CloseDate and others. Now you need Title and Name. So your query string is $select=ProjectName/Title,ProjectName/Name&$expand=ProjectName
- Now you can
$filter where ProjectName/Title="X" or ProjectName/Name="Y". Remember you can not $filter something directly like ProjectName="X". So your $filter should look like $filter=Active eq true and ProjectName/Title eq 'X'
Let me know for more explanation OR have a look on my article
CRUD Operation to List Using SharePoint 2013 Rest API
