Repo.get!() a specific column value from a result row

Questions / Help
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1

I’m getting my all row data using this command: Repo.all
Its returning me whole row by specific search.

ABC_TABLE
    |> where(another_table_id: ^another_table.id)
    |> Repo.all

Is it possible if I don’t take whole row just a specifc col value from resulted row?
Like this:

ABC_TABLE
    |> where(another_table_id: ^another_table.id)
    |> Repo.get!(name_only)

Seeking solution!

2

You might look at select.

3

I can’t find the way to adjust the SELECT PARAM inside my function. So, is there any function of Repo.get!(get_name_only)?

4

Can you should what you have tried?

5

This is my overall function:

 def subscriber_wallet_for_stream(%Stream{} = stream) do
    # Subscriber
    # |> where(stream_id: ^stream.id)
    # |> Repo.get!(:wallet_id)

    SELECT wallet_id FROM Subscriber
      WHERE stream_id = ^stream.id
  end

Just need any possible solution where I can call a single value of column of resulted search row using REPO.GET

6

Ecto mirrors SQL quite closely so if you examine the difference between your SQL statement and your Ecto expression you can see you are missing a |> select(....) expression in your pipeline. But equally, your commented code isn’t a valid Ecto expression so I suggest you revisit the query documentation to see how to construct a query.

2 Likes
7

You might have a look at the link provided, there are some examples…

8

Thank you so much @kokolegorille @kip for helping.
I go through the doc and finally developed the query:

 Repo.all(from s in Subscriber, where: s.stream_id == ^stream.id, select: s.wallet_id)
9

Well done. You could also do Repo.one if you just want a single result, not a list. However if the query returns more than one result then an exception will be raised.

2 Likes