If the member already exists increment its score by <i>increment</i>, otherwise add the member setting <i>increment</i> as score  </td></tr><tr><td style="border: 1px solid #aaa; padding: 5px;"> <a href="ZrankCommand.html">ZRANK</a>  </td><td style="border: 1px solid #aaa; padding: 5px;"> <i>key</i> <i>member</i>  </td><td style="border: 1px solid #aaa; padding: 5px;">  Return the rank (or index) or <i>member</i> in the sorted set at <i>key</i>, with scores being ordered from low to high  </td></tr><tr><td 