title: AWS DYNAMO DB query with multiple condition
body: <p>I am trying to fetch details from dynamo db using the bellow query in this DOMAIN and SERVICE are just key(non primary key)</p>
  
  <pre><code>let params = {
      TableName: asset_table,
      ConsistentRead: true,
      ProjectionExpression: 'ID,SERVICE',
      KeyConditionExpression: "DOMAIN = :service_name AND SERVICE EQ :service_domain",
      ExpressionAttributeValues: {
           ":service_name": {"S":service },
           ":service_domain": {"S":domain}
      }
  };
  docClient.scan(params, (err, data) =&gt; {
      if (err) {
          onComplete(err);
      } else {
          console.log(data);
          onComplete(null, {
              data
          });
      }
  });
  </code></pre>
  
  <p>this give error as given bellow </p>
  
  <pre><code>{
  "message": "ExpressionAttributeValues can only be specified when using expressions: FilterExpression is null",
  "code": "ValidationException",
  "time": "2019-01-09T09:47:09.180Z",
  "requestId": "0G3C02E6251S2H1IQ2LQUTN04JVV4KQNSO5AEMVJF66Q9ASUAAJG",
  "statusCode": 400,
  "retryable": false,
  "retryDelay": 8.070453867451622
   }
  </code></pre>