How to Select Rows with Duplicate Field Values in Django?

Selecting Rows with Duplicate Field Values in Django

To select all rows from a model that have at least one duplicate value for a given field, you can use a combination of Django's aggregation and filtering capabilities:

1. Aggregate values: Use the annotate() method to calculate the count of duplicate values for the specified field. For example, for a model with a name field:

from django.db.models import Count
dupes = Literal.objects.values('name').annotate(id_count=Count('id'))

2. Filter based on count: Use the filter() method to select rows where the count exceeds 1. This will return a ValuesQuerySet containing the duplicated values:

dupes = dupes.filter(id_count__gt=1)

3. Fetch complete records: To obtain the complete records, use the in filter to select rows where the name field matches the duplicated values:

dupes = Literal.objects.filter(name__in=[item['name'] for item in dupes])

Alternative SQL Solution:

If preferred, you can also use a subquery to achieve the same result:

SELECT *
FROM literal
WHERE name IN (
    SELECT name
    FROM literal
    GROUP BY name
    HAVING COUNT(*) > 1
);

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