Elixir Engine

Databases

Elixir Ecto Queries

Building Ecto Queries

Elixir Ecto queries use Query DSL for typed database access.

Introduction to Ecto Queries

Ecto is a powerful database wrapper and query generator for Elixir. At its core, it uses a Domain-Specific Language (DSL) that allows developers to interact with databases in a typed and efficient manner. In this section, we'll explore how to construct queries using Ecto's Query DSL, providing examples for better understanding.

Setting Up Ecto in Your Elixir Project

Before you can start querying databases with Ecto, you need to set up Ecto in your Elixir project. This involves adding Ecto and a database adapter to your dependencies, configuring your repository, and creating a migration.

Here's how you can add Ecto and PostgreSQL adapter to your mix.exs file:

After adding your dependencies, run mix deps.get to fetch them. Next, configure your repository in config/config.exs:

Creating a Simple Query

To perform queries in Ecto, you typically use the from macro. The simplest query fetches all records from a table. Below is an example showing how to query all records from a table named users.

Filtering with Where Clauses

To filter records, you can use the where clause within your query. Here is an example of fetching users with an age greater than 18:

Ordering and Limiting Results

Ecto also supports ordering and limiting results. Use the order_by and limit clauses to refine your query.

Combining Queries with Joins

Joins allow you to combine rows from two or more tables based on a related column. Here's how to perform a join between a users table and a posts table:

Conclusion

Elixir's Ecto queries provide a robust DSL for interacting with databases, making it easier to write complex queries in a readable and maintainable way. With these basics, you can start building efficient database queries in your Elixir applications.

In the next post, we'll dive into Ecto Associations and how they can be used to manage relationships between different entities.

Databases

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Ecto Associations