如何在Django中从关联表获取数据？请求获取员工及对应工作时间

Hey there! Let's get you all the staff information along with their corresponding operating hours. Based on your Django models, here are a few practical approaches to achieve this:

1. Basic Query (Simple but May Cause N+1 Issues) #

You can first fetch all staff members, then iterate through each to access their related operating hours via the days related name:

# Fetch all staff records
all_staff = Staff.objects.all()

# Loop through each staff and display their details + hours
for staff in all_staff:
    print(f"Staff: {staff.name} {staff.last_name}")
    print("Operating Hours:")
    for hours_entry in staff.days.all():
        # Convert day integer to readable name using your constants
        day_label = dict(constants.DAYS).get(hours_entry.day, "Unknown Day")
        print(f"- {day_label}: {hours_entry.start_time} to {hours_entry.end_time}")

2. Optimized Query (Avoid N+1 with Prefetch Related) #

If you have a large number of staff members, using prefetch_related is better—it fetches all related operating hours in a single additional query, boosting performance:

# Prefetch all related operating hours upfront
all_staff = Staff.objects.prefetch_related('days').all()

# Same iteration logic as above, but with fewer database hits
for staff in all_staff:
    print(f"Staff: {staff.name} {staff.last_name}")
    print("Operating Hours:")
    for hours_entry in staff.days.all():
        day_label = dict(constants.DAYS).get(hours_entry.day, "Unknown Day")
        print(f"- {day_label}: {hours_entry.start_time} to {hours_entry.end_time}")

3. Filtered Operating Hours (Optional) #

If you only need specific subsets of hours (e.g., weekday hours), use Prefetch to filter the related records during fetch:

from django.db.models import Prefetch

# Define your filtered queryset (adjust day values to match your constants)
weekday_hours = OperatingHours_staff.objects.filter(day__in=[1, 2, 3, 4, 5])

# Prefetch only the filtered hours, stored under a custom attribute
all_staff = Staff.objects.prefetch_related(
    Prefetch('days', queryset=weekday_hours, to_attr='weekday_days')
).all()

# Access the filtered hours
for staff in all_staff:
    print(f"Staff: {staff.name} {staff.last_name}")
    print("Weekday Operating Hours:")
    for hours_entry in staff.weekday_days:
        day_label = dict(constants.DAYS).get(hours_entry.day, "Unknown Day")
        print(f"- {day_label}: {hours_entry.start_time} to {hours_entry.end_time}")

Hope this helps you get exactly the data you need! 😊

内容的提问来源于stack exchange，提问作者pratik veer