How to pin the top header row showing column names in this bootstrap-vue table?

I have a bootstrap-vue table that looks like this;

Here is the code;

<template>
  <div>
    <b-table hover :items="items"></b-table>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        items: [
          { age: 40, first_name: 'Dickerson', last_name: 'Macdonald' },
          { age: 21, first_name: 'Larsen', last_name: 'Shaw' },
          {
            age: 89,
            first_name: 'Geneva',
            last_name: 'Wilson',
            _rowVariant: 'danger'
          },
          {
            age: 40,
            first_name: 'Thor',
            last_name: 'MacDonald',
            _cellVariants: { age: 'info', first_name: 'warning' }
          },
          { age: 29, first_name: 'Dick', last_name: 'Dunlap' }
        ]
      }
    }
  }
</script>

Suppose the table has many rows. I would like to pin the top header row such that when I scroll down the table, the header row showing the column names remains at the top. This makes the table more readable.

The table code was provided in bootstrap-vue documentation.

https://bootstrap-vue.org/docs/components/table

I am using Vue v2.6 and BootstrapVue.

Solution

BootstrapVue's table provides sticky-header prop for this purpose.

As outlined in the documentation, using

<b-table :sticky-header="true">
  ...table contents here
</b-table>

sets the height of the table to 300px
sets table's overflow to auto
sets table's position to relative
sets position to sticky (z-index to 2 and position to relative) for each <th /> in the table header

Important: the above are required for the table header to be sticky relative to the table, not to the entire page. If you use @LajosArpad's solution, the table will be sticky in relation to the page, and when scrolling past the table the table header will remain visible, which is probably not the desired result.

If you want the table to have any other height than 300px, you have to pass it as the value of sticky-header prop:

<b-table sticky-header="80vh">
  ...table contents here
</b-table>

See it working on codesandbox.