长下拉菜单不是列表-如何使其滚动？

Question

我想实现我在this site和this fiddle上阅读的内容，但是我真的不明白如何使它工作。

这是我的菜单。我将代码上的类更改为菜单的类，但是没有用。我也没有列表类型菜单。

SELECT Cast(EventDate As Date) As SummaryDate,
       SUM(CASE WHEN EventType = 'Failed' THEN 1 ELSE 0 END) As Failures,
       SUM(CASE WHEN EventType = 'Inbound' THEN 1 ELSE 0 END) As Inbounds,
       SUM(CASE WHEN EventType = 'Outbound' THEN 1 ELSE 0 END) As Outbounds
FROM tblTests
GROUP BY Cast(EventDate As Date)

Answer 1

.dropdown-content{
    max-height: 100px;
    overflow-y: auto;
}