CODEWITHSUNDEEP
ruby-on-railspostgresqlheroku
DeLaFuente
DeLaFuente

Reputation: 75

Error with group(...) from SQlite to PostgreSQL in Rails

I'm trying to upload my app to heroku but it gives me an error in this statement:

@exhibition.enrolments.select(:id).group('payment_id')

ActiveRecord::StatementInvalid (PG::GroupingError: ERROR: column "enrolments.id" must appear in the GROUP BY clause or be used in an aggregate function

In SQlite I didn't have any errors, but in Production I have it.

The question is: I have this:

enrolment_id | payment_id | ....
1            | 1          | ....
2            | 1          | ....
3            | 2          | ....
4            | 3          | ....
5            | 3          | ....

And I want to get the enrolments' ids 2,3 and 4.

I tried this too:

@exhibition.enrolments.select(:id).group('enrolment.id, payment_id')

It works but it just gives me all entries, obviously...

I read to many posts about this but I didn't get the solucion...

Any help? Thank you.

EDIT:

I mean:

And I want to get the enrolments' ids 2,3 and 5.

The greatest enrolment_id in each block of payments with the same id.

Thx Frank Heikens

Upvotes: 0

Views: 74

Answers (1)

TomDunning
TomDunning

Reputation: 4877

So give it the aggregate function it wants?

@exhibition.enrolments.select(:id).group('payment_id').max(:id)

Alternatively, you could order the records and use distinct

@exhibition.enrolments.order('payment_id DESC').select(:payment_id).distinct

Upvotes: 1

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