表格边框有一边有缝隙的问题

img

img


为什么这个边框右边会有一个缝隙，新手上路真的不知道问题出在哪里

表格（如果有启用border）外边框始终会存在一层border
通过背景色遮挡缝隙

table {
  background-color: black;
}
tr {
  background-color: white;
}

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      table {
        background-color: black;
      }
      tr {
        background-color: white;
      }
    </style>
  </head>
  <body>
    <table
      align="center"
      border="1"
      cellpadding="10px"
      cellspacing="0px"
      width="500"
      height="249"
    >
      <tr>
        <th>及格否</th>
        <th>姓名</th>
        <th>分数</th>
      </tr>
      <tr>
        <th>及格</th>
        <th>小明</th>
        <th>88</th>
      </tr>
      <tr>
        <th>及格</th>
        <th>小红</th>
        <th>86</th>
      </tr>
      <tr>
        <th>不及格</th>
        <th>小军</th>
        <th>56</th>
      </tr>
    </table>
  </body>
</html>