切换SQL显示详细信息

Question

我创建了一个按钮并运行sql来显示所有onleave细节：

<input type="button" style="cursor: pointer;width:180px;" value="Show All Onleave Detail">

如何创建切换功能？首先sql运行为：

$sql = "SELECT * FROM onleave where DATE(o_to) >= CURDATE() ORDER BY o_from DESC";

单击按钮时，sql将更改为：

$sql = "SELECT * FROM onleave ORDER BY o_from DESC";