I just want do execute an Ecto query with an simple concatination of two or more columns.
I think the following elixir pseudo code already shows what I try to do:
customers = Customer.undeleted(
from c in Customer,
select: %{id: c.id, name: c.name <> " – " <> c.street},
order_by: c.name
) |> Repo.all
It drives me crazy cuz in SQL it is easy like this: ...SELECT c.id, concat(c.name, ' - ', c,street) AS name
Any ideas how to solve this with ecto querys ?
You cannot use <> in a select expression in Ecto. If you want to call concat like that, you can use fragment:
select: %{id: c.id, name: fragment("concat(?, ' - ', ?)", c.name, c.street)},
To add to @Dogbert answer, you can clean up the code a bit by putting the SQL function fragment in a custom macro as described in the docs:
defmodule CustomSQLFunctions do
defmacro concat(left, mid, right) do
quote do
fragment("concat(?, ?, ?)", unquote(left), unquote(mid), unquote(right))
end
end
end
Then import for use in query
import CustomSQLFunctions
customers = Customer.undeleted(
from c in Customer,
select: %{id: c.id, name: concat(c.name, ' - ', c.street)},
order_by: c.name
) |> Repo.all
