一对多需要使用外键
一：外键创建ForeignKey
b=models.ForeignKey(to="Business",to_field=("id"))#django会在生成表的时候变为b_id
to表示和那个表关联，to_field没有和那个字段关联，不写默认是id
from django.db import models # Create your models here. class Foo(models.Model):
name=models.CharField(max_length=32) class Business(models.Model):
caption=models.CharField(max_length=32)
code=models.CharField(max_length=32,null=True,default="SA")
fk=models.ForeignKey(to="Foo",to_field=("id"))#默认会和主键关联 class Host(models.Model):
nid=models.AutoField(primary_key=True)
hostname=models.CharField(max_length=32,db_index=True)
ip=models.GenericIPAddressField(protocol='ipv4',db_index=True)
port=models.IntegerField()
b=models.ForeignKey(to="Business",to_field=("id"))
二：一对多数据创建
一对多数据创建有两种方式
1)使用对象创建
Host.objects.create(
hostname="host1",
ip="1.1.1.1",
port="",
b=Business.objects.filter(id=1).first(),)
2）直接使用外建字段_id创建
Host.objects.create(
hostname="host1",
ip="1.1.1.1",
port="",
b_id=1,) #外键创建时候会自动把字段b建立成b_id字段，可以直接赋值。这种方法好于第一种，原因不需要连表查询，推荐第二种
三：一对多数据查询
一对多数据查询有两种形式
1）queryset内容为对象
Host.objects.filter(nid__gt=0)
Host.objects.all()等
host_list=Host.objects.all()
for row in host_list:
print(row.b_id) #直接访问b_id
print(row.b) #这个是Business对象，所以访问下面的字段
print(row.b.caption)
2)查询使用values和values_list指定字段，使用row.b.caption会直接报错。这里可以使用双下线跨表查询.
3)查询使用values_list指定字段，使用row.b.caption会直接报错。这里可以使用双下线跨表查询.
注：values返回是字典，values_list返回是元组
示例如下： views
def host1(request):
v1=Host.objects.filter(nid__gt=0) #v1=Host.objects.filter(nid__gt=0)
# v1=Host.objects.filter(nid__gt=0).values("nid","hostname","b_id","b.caption") #b.caption不能跨表直接报错
v2=Host.objects.filter(nid__gt=0).values("nid","hostname","b_id","b__caption") #两个下划线可以实现跨表
#filter(nid__gt=0).values("nid","hostname","b_id","b__caption")相跨表都用双下划线
#queryset对象内部为字典
for row in v2:
print(row["nid"],row["hostname"],row["b_id"],row["b__caption"]) v3=Host.objects.filter(nid__gt=0).values_list("nid","hostname","b_id","b__caption")
return render(request,"host.html",{"v1":v1,"v2":v2,"v3":v3})
模板代码：
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/html">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.shade {
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
background-color: #333333;
opacity: 0.6;
z-index: 9;
} .add-mode {
position: fixed;
height: 300px;
width: 400px;
top: 100px;
left: 50%;
margin-left: -200px;
z-index: 11;
background-color: white;
} .hide {
display: none;
}
</style>
</head>
<body>
<input type="button" value="增加" id="add_host"> <h1>主机列表（对象）</h1>
<table border="1px">
<thead>
<tr>
<th>序号</th>
<th>主机名</th>
<th>主机地址</th>
<th>端口</th>
<th>业务线名称</th> </tr>
</thead>
<tbody>
{% for row in v1 %}
<tr host-id="{{ row.nid }}" bid="{{ row.b_id }}">
<td>{{ forloop.revcounter }}</td>
<td>{{ row.hostname }}</td>
<td>{{ row.ip }}</td>
<td>{{ row.port }}</td>
<td>{{ row.b.caption }}</td>
</tr>
{% endfor %} </tbody>
</table>
<h1>主机列表（字典）</h1>
<table border="1px">
<thead>
<tr>
<th>主机名</th>
<th>主机地址</th>
<th>端口</th>
<th>业务线名称</th>
</tr>
</thead>
<tbody>
{% for row in v2 %}
<tr host-id="{{ row.nid }}" bid="{{ row.b_id }}">
<td>{{ row.hostname }}</td>
<td>{{ row.ip }}</td>
<td>{{ row.port }}</td>
<td>{{ row.b__caption }}</td>
</tr>
{% endfor %}
</tbody>
</table>
<h1>主机列表（元组）</h1>
<table border="1px">
<thead>
<tr>
<th>主机名</th>
<th>主机地址</th>
<th>端口</th>
<th>业务线名称</th>
</tr>
</thead>
<tbody>
{% for row in v3 %}
<tr host-id="{{ row.nid }}" bid="{{ row.b_id }}">
<td>{{ row.0 }}</td>
<td>{{ row.1 }}</td>
<td>{{ row.2 }}</td>
<td>{{ row.3 }}</td>
</tr>
{% endfor %}
</tbody>
</table>
<table border="1px">
<thead>
<tr>
<th>序号</th>
<th>主机名</th>
<th>主机地址</th>
<th>端口</th>
<th>业务线名称</th> </tr>
</thead>
<tbody>
{% for i in v1 %}
{% for row in v1 %}
<tr host-id="{{ row.nid }}" bid="{{ row.b_id }}">
<td>{{ forloop.parentloop }}</td>
<td>{{ row.hostname }}</td>
<td>{{ row.ip }}</td>
<td>{{ row.port }}</td>
<td>{{ row.b.caption }}</td>
</tr>
{% endfor %}
{% endfor %} </tbody>
</table>
<!--模态对话框实现增加主机信息-->
<div class="shade hide"></div>
<div class="add-mode hide">
<form action="/host" method="post">
<div class="group">
<input type="text" name="hostname" placeholder="请输入主机名">
</div>
<div class="group">
<input type="text" name="ip" placeholder="请输入主机IP">
</div>
<div class="group">
<input type="text" name="port" placeholder="请输入主机端口">
</div>
<!--绑定businss信息-->
<div class="group">
<select name="group_id">
{% for group in v4 %}
<option value="{{ group.id }}">{{ group.caption }}</option>
{% endfor %}
</select>
</div>
<div class="group">
<input type="submit" value="提交">
<input type="button" value="取消">
</div>
</form>
</div> <script src="/static/jquery-1.12.4.js"></script>
<script>
$("#add_host").click(
function () {
$(".shade,.add-mode").removeClass("hide")
}
)
</script>
</body>
</html>