Django QuerySet使用Postgres数据库的特定类型，唯一外国ID的当天获取列表

Question

我正在尝试找到一个查询，以获取特定日期的最新出勤列表，而独特的员工已签入（checkin = 1）

以下是我的模型，记录和我要完成的目标。

我的型号有2个模型：

class Employee(models.Model):
    fullname = models.CharField(max_length=30, blank=False)    
class Attendance(models.Model):
    CHECKIN = 1
    CHECKOUT = 2
    ATTENDANCE_TYPE_CHOICES = (
        (CHECKIN, "Check In"),
        (CHECKOUT, "Check Out"),
    )
    employee = models.ForeignKey(Employee)
    activity_type = models.IntegerField(choices = ATTENDANCE_TYPE_CHOICES, default=CHECKIN)
    timestamp = models.DateTimeField(auto_now_add=True)

假设我有以下记录：

Employee
{"id":1, "employee":"michael jackson",
"id":2, "fullname":"mariah carey",
"id":3, "fullname":"taylor swift"}
Attendance
{"id":1, "employee": 1,"activity_type": 1, timestamp: "2017-12-05 09:08", -interested in this for the activity type (1 for CHECKIN) and the date 2017-12-05, last of that employee id for that day
"id":2, "employee": 2,"activity_type": 1, timestamp: "2017-12-05 10:13",
"id":3, "employee": 3,"activity_type": 1, timestamp: "2017-12-05 11:30",
"id":4, "employee": 2,"activity_type": 2, timestamp: "2017-12-05 15:13", 
"id":5, "employee": 3,"activity_type": 2, timestamp: "2017-12-05 18:30", 
"id":6, "employee": 2,"activity_type": 1, timestamp: "2017-12-05 19:13", -interested in this for the activity type (1 for CHECKIN) and the date 2017-12-05, last of that employee id for that day
"id":7, "employee": 3,"activity_type": 1, timestamp: "2017-12-05 20:30", -interested in this for the activity type (1 for CHECKIN) and the date 2017-12-05, last of that employee id for that day
"id":8, "employee": 1,"activity_type": 2, timestamp: "2017-12-06 08:08"}

我是兴趣，因此它仅根据Checkin的活动类型1和2017-12-05的活动类型1输出这2个记录，并且该员工ID必须是唯一且最新的：

{"id":1, "employee": 1,"activity_type": 1, timestamp: "2017-12-05 09:08",
"id":6, "employee": 2,"activity_type": 1, timestamp: "2017-12-05 19:13"
"id":7, "employee": 3,"activity_type": 1, timestamp: "2017-12-05 20:30"}

我正在使用Postgres 9.4

如何使用django queryset产生预期的结果？

Answer 1

activity_type的过滤出勤率， employee_id和 -timestamp订购，然后在 employee_id

上使用不同

Attendance.objects.filter(activity_type=Attendance.CHECKIN).order_by('employee_id','-timestamp').distinct('employee_id')