y to a string returning the old value of the key  </td></tr><tr><td style="border: 1px solid #aaa; padding: 5px;"> <a href="SetnxCommand.html">SETNX</a>  </td><td style="border: 1px solid #aaa; padding: 5px;"> <i>key</i> <i>value</i>  </td><td style="border: 1px solid #aaa; padding: 5px;">  Set a key to a string value if the key does not exist  </td></tr><tr><td style="border: 1px solid #aaa; padding: 5px;"> <a href="SetexCommand.html">SETEX</a>  </td><td style="border: 1px solid #aaa; padding: 5px;"> <i>ke