Question

我是新来的休眠对象，需要使用名为 channel_id 的表 channels 的外键为表 transactions 建立主键以及每个 channel_id 的自动生成的序列。

例如：

<!DOCTYPE HTML>
<html>
<head>
<style>

.sectionP
{
            width:100px;
            height:200px;
}

.section1,.section2,.section3,.section4
{

            width:200px;
            height:200px;
            position:absolute;
}

.section3,.section4
{
            z-index:10;
}

</style>
<script>
function allowDrop(ev) {
  ev.preventDefault();
}

function drag(ev) {
  ev.dataTransfer.setData("text", ev.target.id);
}

function drop(ev) {
  ev.preventDefault();
  var data = ev.dataTransfer.getData("text");
  ev.target.appendChild(document.getElementById(data));
}
</script>
</head>
<body>

<h2>Drag and Drop</h2>
<p>Drag the image back and forth between the two div elements.</p>

<section id ="sectionP">
    <section id = "section1">
 <svg width="200" height="200" id="svg1">
      <circle id="cir1" cx="100" cy="100" r="80" 
      stroke="green" stroke-width="4" fill="white">
   </circle>
   </svg>
   </section>
       <section class ="section3" width="200" height="200" ondrop="drop(event)" ondragover="allowDrop(event)"></section>
   <section id = "section2">
    <svg width="200" height="200" id="svg2">
   <circle id="cir2" cx="100" cy="100" r="80" 
      stroke="yellow" stroke-width="4" fill="white">
</circle>
         </svg>
   </section>

    <section class ="section4" width="200" height="200" ondrop="drop(event)" ondragover="allowDrop(event)"></section>
    </section>
<section>
 <img src="img_w3slogo.gif" draggable="true" ondragstart="drag(event)" id="drag1" width="88" height="31">
</section>

</body>
</html>

序列 transaction_id 应该从1开始并在同一 channel_id 内以1 递增：

TABLE channels { channel_id ....Other channels fields PK (channel_id) } TABLE transactions { transaction_id channel_id ...Other transactions fields PK(transaction_id, channel_id) FK(channel_id) }

如果相关，我使用MySQL 8.0.17

如何在休眠中将外键和自动生成的值定义为主键

0 个答案: