Find duplicate entries in database for specific fields

Question

I have model having fields as name, school, email, address etc.

I want to find out the rows for which there is same entry for name and school field ?

eg:
name school email 
abc     mps    abc@gmail.com
abc     mps    abc@gmail.com
xyz     vps    xyz@gmail.com
abc     mps    abc@gmail.com
poi     vps    poi@gmail.com
jkl     vps    jkl@gmail.com

like for name abc and school mps ther are 3 entries and for xyz and vps there are 2 entries I can nested for loop and iterative manner to check the name and school fields against all the rows in the table. That would be performance hit (n*n)

Is there any other way to find out ?

do you have the name and school you are looking for or do you want to get all counts name/school combinations? — dm03514, May 28 '14 at 16:20
I think it's solved here http://stackoverflow.com/questions/8989221/django-select-only-rows-with-duplicate-field-values Basically you group by name or school and then check if count > 1 — FrEaKmAn, May 28 '14 at 16:21

score 0 · Accepted Answer · answered May 28 '14 at 10:42

0

distinct() will serve the purpose. The following will solve your problem

model_name.objects.values_list('name').distinct()

If you want dictionary then you have to do this

model_name.objects.values('name').distinct()

Hope that solves you issue!!

answered May 28 '14 at 10:42

S.Ali

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@FrEaKmAn "Returns a new QuerySet that uses SELECT DISTINCT in its SQL query. This eliminates duplicate rows from the query results." thats what the official docs say when you goto the link that i have mentioned – S.Ali May 28 '14 at 16:26
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but how does this solve the question I want to find out the rows for which there is same entry for name and school field ? – FrEaKmAn May 29 '14 at 12:59

AlvaroAV · Answer 2 · 2014-05-30T10:36:18.117

I'm not sure if I understand you, you just want to get the results wich has the SAME name and school, or just want to get ONE result for name and school ?

This sentence will return ALL schools with name 'abc' and school 'mps'

result_list = model.objects.filter(name='abc').filter(school='mps')

If you're trying to get only ONE result per name and school, you have to use distinct() like:

result_list = model.objects.filter(name='abc').filter(school='mps').distinct() `

Find duplicate entries in database for specific fields

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