title: How do I use the Loopback where filter correctly on REST-API
body: <p>Hi there I seem to miss some information about Loopback where clause or syntax. My problem is, that I receive an empty array if I try to get a list of matching model instances, does no difference if in loopback api explorer or trhough http api request.</p>
  
  <p>My "subject" model:</p>
  
  <pre><code>[
    {
      "user": "string",
      "semester": "string",
      "subject_name": "string",
      "subject_relevance": 1,
      "subject_details": 0,
      "id": "string"
    }
  ]
  </code></pre>
  
  <p>One Instance of Subjects:</p>
  
  <pre><code>{
    "user": "59eef907cc199c1cf8f99296",
    "semester": "59eef6f8ebf12e1a37ee898b",
    "subject_name": "Mathematik",
    "subject_relevance": "1",
    "subject_details": "",
    "id": "59eef96aebf12e1a37ee898f"
  }
  </code></pre>
  
  <p>My Loopback API Explorer filter:</p>
  
  <pre><code>{"where" : {"semester" : "59eef6f8ebf12e1a37ee898b"}}
  </code></pre>
  
  <p>My http request:</p>
  
  <pre><code>http://localhost:3000/api/subjects?filter[where][semester]=59eef6f8ebf12e1a37ee898b
  </code></pre>
  
  <p>The result I receive:</p>
  
  <pre><code>[]
  </code></pre>
  
  <p>If I try to search for this:</p>
  
  <pre><code>{"where" : {"subject_name" : "Mathematik"}}
  </code></pre>
  
  <p>or in browser:</p>
  
  <pre><code>http://localhost:3000/api/subjects?filter[where][subject_name]=Mathematik
  </code></pre>
  
  <p>I reveive the instance correctly or as expected. So I went thrugh the <a href="https://loopback.io/doc/en/lb3/Where-filter.html" rel="nofollow noreferrer">documentation</a> and I strugle to find some hints or solutions to my problem. Can someone help me out or suggest me something to get the right instance back? Do I miss something? Has it to do that these are ID-fields or what is it?</p>
  
  <p>Thanks for any help in advance!!</p>