title: Unable to update to existing value in DynamoDb
body: <p>I have a table in dynamodb with key as word and value as cou. word is my hash key and cou is the attribute key. I am trying to update one of my word value to another value. I am getting this exception.</p>
  
  <pre><code>com.amazonaws.AmazonServiceException: The provided key element does not match the schema
  </code></pre>
  
  <p>What I am doing is in the below code. Any suggestions. </p>
  
  <pre><code>java.util.Map&lt;String, AttributeValue&gt; item = new HashMap&lt;String, AttributeValue&gt;();
              item.put("word", new AttributeValue().withS("TimeZone"));
  
              java.util.Map&lt;String, AttributeValue&gt; expressionAttributeValues = new HashMap&lt;String, AttributeValue&gt;();
              expressionAttributeValues.put(":val1", new AttributeValue().withN("1"));
              expressionAttributeValues.put(":val2", new AttributeValue().withN("12"));
  
              ReturnValue returnValues = ReturnValue.ALL_NEW;
  
              UpdateItemRequest updateItemRequest = new UpdateItemRequest()
                  .withTableName(tableName)
                  .withKey(item)
                  .withUpdateExpression("add cou :val1 set NewAttribute=:val2")
                  .withExpressionAttributeValues(expressionAttributeValues)
                  .withReturnValues(returnValues);       
  
              UpdateItemResult result = client.updateItem(updateItemRequest);
  </code></pre>