Implemented for both atoms (like User) and strings (like 'users'). On the right-hand side of in, we passed the query itself.Īny value can be used on the right-hand side of in as long as it implements The difference is that, instead of passing a schema like User nameĬomposing queries uses the same syntax as creating a query. age > 18 # Extend the query query = from u in query, select : u. For example, the query above canĪctually be defined in two parts: # Create a query query = from u in User, where : u. Use is_nil/1 instead: from u in User, where : is_nil ( u. This is done as a security measure to avoid attacks that attempt Nil comparison in filters, such as where and having, is forbiddenĪnd it will raise an error: # Raises if age is nil from u in User, where : u. Remember Ecto does not require them in order to write queries. age > ^ age )įor this reason, we will use schemas on the remaining examples but The select option in queries, as by default Ecto will retrieve allįields specified in the schema: age = '18' Repo. name )Īnother advantage of using schemas is that we no longer need to specify In such cases, Ecto will analyze your queries andĪutomatically cast the interpolated 'age' when compared to the u.ageįield, as long as the age field is defined with type :integer in To avoid the repetition of always specifying the types, you may defineĪn Ecto.Schema. In the example above, Ecto will cast the age to type integer. age > type ( ^ age, :integer ), select : u. What is the expected type of the value being interpolated: age = '18' Repo. When interpolating values, you may want to explicitly tell Ecto height > ^ ( height_ft * 3.28 ), select : u. Arrays:, ~w(interpolate words)Īll other types and dynamic values must be passed as a parameter usingĮxternal values and Elixir expressions can be injected into a queryĮxpression with ^: def with_minimum ( age, height_ft ) do from u in 'users', where : u.Atoms (other than booleans and nil): :foo, :bar.Strings: 'foo bar', ~s(this is a string).You can find the full list of operations in .īesides the operations listed there, the following literals are > comparison operator and the literal 0: query = from u in 'users', where : u. Query below, for example, we use u.age to access a field, the They are passed as arguments to a function from Ecto.Repo.Įcto allows a limited set of expressions inside queries. Queries do not reach out to the data store until

In the example above, we are directly querying the 'users' tableįrom the database. name # Send the query to the repository Repo. Let's see a sample query: # Imports only from/2 of Ecto.Query import Ecto.Query, only : # Create a query query = from u in 'users', where : u. The macro one will be explored in later sections. Most examples will use the keyword-based syntax, Ecto queries come in two flavors: keyword-basedĪnd macro-based. Queries are used to retrieve and manipulate data from a repository Inside Ecto migrations, we can accomplish this by wrapping the command in an execute().Settings View Source Ecto.Query (Ecto v3.10.3) CREATE INDEX ON reviews((metadata->'item'->'price')) In a large table where a particularly embedded field is important enough to query, such as price in this case, it's a good idea to add an index.

To find all reviews with such a structure and a price of 35, we can do the following: select * from metadata These can be queried in the DB with: select * from metadataĭigging in further we could examine only reviews with an an item field in the metadata and another nested field price. Over time, we might come to find that some reviews include an item field in their metadata. # How do we create an index a JSONB sub-field?Įnd Querying into JSONB fields with raw SQL It's particularly useful for situations involving user-submitted data, where we don't know the exact shape the data will come in.Ĭonsider this schema for user-submitted reviews: defmodule doĪdd :rating, :integer, default: 0, null: falseĬreate(unique_index(:reviews, )) Ecto has a map type, which is implemented in Postgres as a JSONB field.

Elixir ecto postgres select query