We add the :autogenerate option to tell Ecto that the database will be generating “This uses the :id type to indicate that it is an integer-based primary key, and If not a complete reordering … maybe a section up front about how the Ecto modules map to the standard database operations - and that jumping ahead to Ecto.Migration wouldn’t interfer with the understanding when you come back to the book order. The example in the book is great - but I personally learn by doing my own examples - getting in and making mistakes and seeing how it fits together … especially with something that has multiple sections/modules like Ecto - it felt odd having to wait to get to Migrations before I worked out how that worked with ecto.
Elixir ecto select count how to#
I think putting Ecto.Migration first seems a more natural order as that is how one would deal with learning how to interact with a database - How do I create schema in the database - How do I modify schema in the database - How do I create/retrieve/delete records - How do I modify records. Should be snake case.įirstly I love the book - it’s great. Text refers to ‘add_compositions_table’ as camel case. What’s the behavior if we actually deleted two records? The document states: “Raises if more than one entry.” What does that even mean? How does that error looks like? What is exactly Repo.one when deleting? This isn’t “exactly” like inserting operation, the insert and insert all did not user Repo.one at all. Track = Repo.one(from t in Track, where: t.title = “The Moontrane”) I’m not sure how well formatting will work here, but assuming at least pre tags work: get_one_of = fn (vs, default) ->Įnum.reduce(vs, nil, &(&2 || System.get_env(&1))) || default Since homebrew uses the username for the login, I tend to fallback to the username before defaulting to “postgres”. The following configuration allows the user to set up environment variables to configure the database. Otherwise, the text would need to be amended accordingly. The downloaded source has `mix.exs` dependency set to `~> 1.6` when I think it should have been `~> 1.4`. (Mix) You’re trying to run :music_db on Elixir v1.5.2 but it has declared in its mix.exs file it supports only Elixir ~> 1.6 Running the `mix do deps.get, compile` command yields an error with Elixir 1.5.2 or it seems potentially with any Elixir version down to 1.4 despite the statement “To start, you’ll need Elixir 1.4 or greater, and a database that can support Ecto 2.2 (we recommend Postgres …” These work the same way ask they do in associations,… Last sentence of “Making Changes” section. The add function… There’s no sensisble default… We will be taking a closer look at this shortly, and we'll definitely have everything working before the book goes into production. I apologize for not having addressed this sooner. (ecto) lib/ecto/adapters/mysql.ex:107: _ddl/3 (ecto) lib/ecto/adapters/mysql/connection.ex:529: .execute_ddl/1 (ecto) lib/ecto/adapters/mysql/connection.ex:769: .intersperse_map/4 (ecto) lib/ecto/adapters/mysql/connection.ex:622: .column_definition/2 (ecto) lib/ecto/adapters/mysql/connection.ex:692: .column_type/2 (ecto) lib/ecto/adapters/mysql/connection.ex:806: .error!/2 (ArgumentError) Array type is not supported by MySQL
In fact, I get the following error when running “mix ecto migrate” under MariaDB 10.2.14 : I don’t think MySQL can be used with the given source code, since the table “albums_with_embeds” has an array, and MySQL does not support them (?). “To start, you’ll need Elixir 1.4 or greater, and a database that can supportĮcto 2.2 (we recommend Postgres, but you can also use MySQL)” This error is telling us that one or more of our artists records cannot be deletedīecause there are other records that refer to them. But remember that you can restoreĪll the app’s sample data by exiting out of IEx and running mix ecto.reset on “If you just ran this command in IEx (and we hope you have), you just deletedĪll the records in the tracks table.
Elixir ecto select count code#
This works greatįor one- or two-line examples.” No code in previous section “You can open up an IEx session with iex -S mix as we did in the last section,Īnd type or copy/paste the code directly into the console. MusicDB.Repo, MusicDB.Artist, or use an alias.
Elixir ecto select count full#
”Ĭhange code references to full path, i.e. Should be: “(Artist, :count, :id)”īut I still get an error on execution: “ (Protocol.UndefinedError) protocol Ecto.Queryable not implemented for Artist, the given module does not exist. Last paragraph: “Repo.aggregate(Artist, :count, :id)”
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