Python 检查值是否存在于另一个表中

对不起，我有点怀疑，我是学生。我有这种情况

    class Equipment():
        id
        name 
        ...

    class Alert():
        id
         ...
        pin
        value
       equipment_id

表设备-警报没有关系：

我需要检查警报表中是否存在设备表的id 如果需要返回A，如果没有返回B，则返回th到模板

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很难说你想做什么，但是你可以做一系列的工作

# will give all equipment_ids in all alerts
alerted_equipment_ids = Alert.objects.values_list('equipment_id', flat=True).distinct()

# will filter Equipment and give those with alerts
alerted_equipment = Equipment.objects.filter(pk__in=alerted_equipment_ids)

# will get alerts that has a valid equipment-ID
alerts_for_alerted_equipment = Alert.objects.filter(equipment_id__in=alerted_equipment.values_list('pk', flat=True))

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你试了什么？