phoenix ecto query expression

To perform query expressions in Elixir's Phoenix framework with Ecto, you can use the Ecto.Query module. Here's an example of how to construct a query expression:

Import the necessary modules:

import Ecto.Query

Build the query expression using the from function:

query = from p in Post,
        where: p.author == "John",
        select: p.title

In this example, we are querying the Post table and selecting the title column where the author is "John".

Execute the query using Repo.all or Repo.one:

results = MyApp.Repo.all(query)

This will execute the query and return the results.

You can also perform more complex queries by combining multiple clauses. Here's an example:

query = from p in Post,
        where: p.author == "John" and p.views > 100,
        join: c in Comment, on: c.post_id == p.id,
        select: {p.title, c.body},
        order_by: [desc: p.inserted_at],
        limit: 10

In this example, we are querying the Post table and joining it with the Comment table. We select the title from the Post table and the body from the Comment table. We also order the results by the inserted_at column in descending order and limit the results to 10.

You can further explore the Ecto.Query module to learn about the different query functions and operators available for constructing query expressions in Elixir with Phoenix.