# AyeSQL
 [](https://hex.pm/packages/ayesql) [](https://hex.pm/packages/ayesql) [](https://coveralls.io/github/alexdesousa/ayesql?branch=master)
> **Aye** _/ʌɪ/_ _exclamation (archaic dialect)_: said to express assent; yes.
_AyeSQL_ is a library for using raw SQL.
## Overview
Inspired by Clojure library [Yesql](https://github.com/krisajenkins/yesql),
_AyeSQL_ tries to find a middle ground between strings with raw SQL queries and
SQL DSLs. This library aims to:
- Keep SQL in SQL files.
- Generate easy to use Elixir functions for every query.
- Parameterize queries using maps and keyword lists.
- Allow query composablity.
- Work out-of-the-box with PostgreSQL using
[Ecto](https://github.com/elixir-ecto/ecto_sql) or
[Postgrex](https://github.com/elixir-ecto/postgrex).
If you want to know more about AyeSQL:
- [Small example](#small-example)
- [Syntax](#syntax)
+ [Naming queries](#naming-queries)
+ [Parameters](#parameters)
+ [Mandatory parameters](#mandatory-parameters)
+ [Query composition](#query-composition)
+ [Optional fragments](#optional-fragments)
+ [IN statement](#in-statement)
+ [Subqueries and subfragments](#subqueries-and-subfragments)
- [Installation](#installation)
And the following additional links provide more information about the library:
- [Full Documentation](https://hexdocs.pm/ayesql)
- [AyeSQL: Writing Raw SQL in Elixir](https://thebroken.link/ayesql-writing-raw-sql-in-elixir/)
- [Why raw SQL?](https://hexdocs.pm/ayesql/why-raw-sql.html)
- [Dynamic queries with EEx](https://hexdocs.pm/ayesql/dynamic-queries-with-eex.html)
- [Adding support to other databases](https://hexdocs.pm/ayesql/query-runners.html)
## Small Example
In AyeSQL, the equivalent would be to create an SQL file with the query e.g.
`queries.sql`:
```sql
-- file: queries.sql
-- name: get_avg_clicks
-- docs: Gets average click count.
WITH computed_dates AS (
SELECT datetime::date AS date
FROM generate_series(
current_date - :days::interval, -- Named parameter :days
current_date - interval '1 day',
interval '1 day'
)
)
SELECT dates.date AS day, count(clicks.id) AS count
FROM computed_date AS dates
LEFT JOIN clicks AS clicks ON date(clicks.inserted_at) = dates.date
WHERE clicks.link_id = :link_id -- Named parameter :link_id
GROUP BY dates.date
ORDER BY dates.date;
```
In Elixir, we would load all the queries in this file by creating the following
module:
```elixir
# file: lib/queries.ex
defmodule Queries do
use AyeSQL, repo: MyRepo
defqueries("queries.sql") # File name with relative path to SQL file.
end
```
or using the macro `defqueries/3`:
```elixir
# file: lib/queries.ex
import AyeSQL, only: [defqueries: 3]
defqueries(Queries, "queries.sql", repo: MyRepo)
```
> **Note**: The file name used in `defqueries` macro should be relative to the
> file where the macro is used.
Both approaches will create a module called `Queries` with all the queries
defined in `queries.sql`.
And then we could execute the query as follows:
```elixir
iex> params = [
...> link_id: 42,
...> days: %Postgrex.Interval{secs: 864_000} # 10 days
...> ]
iex> Queries.get_avg_clicks(params)
{:ok,
[
%{day: ..., count: ...},
%{day: ..., count: ...},
%{day: ..., count: ...},
...
]
}
```
## Syntax
An SQL file can have as many queries as you want as long as they are named.
For the following sections we'll assume we have:
- `lib/my_repo.ex` which is an `Ecto` repo called `MyRepo`.
- `lib/queries.sql` with SQL queries.
- `lib/queries.ex` with the following structure:
```elixir
import AyeSQL, only: [defqueries: 3]
defqueries(Queries, "queries.sql", repo: MyRepo)
```
### Naming Queries
For naming queries, we add a comment with the keyword `-- name: ` followed by
the name of the function e.g the following query would generate the function
`Queries.get_hostnames/2`:
```sql
-- name: get_hostnames
SELECT hostname FROM server
```
Additionally, we could also add documentation for the query by adding a comment
with the keyword `-- docs: ` followed by the query's documentation e.g:
```sql
-- name: get_hostnames
-- docs: Gets hostnames from the servers.
SELECT hostname FROM server
```
> Important: if the function does not have `-- docs: ` it won't have
> documentation e.g. `@doc false`.
### Parameters
There are two types of parameters:
- Mandatory: for passing parameters to a query. They start with `:` e.g.
`:hostname`.
- Optional: for query composability. They start with `:_` e.g. `:_order_by`.
Additionally, any query in a file can be accessed with its name adding `:` at
the front e.g `:get_hostnames`.
### Mandatory Parameters
Let's say we want to get the name of an operative system by architecture:
```sql
-- name: get_os_by_architecture
-- docs: Gets operative system's name by a given architecture.
SELECT name
FROM operative_system
WHERE architecture = :architecture
```
The previous query would generate the function
`Queries.get_os_by_architecture/2` that can be called as:
```elixir
iex> Queries.get_os_by_architecture(architecture: "AMD64")
{:ok,
[
%{name: "Debian Buster"},
%{name: "Windows 10"},
...
]
}
```
### Query Composition
Now if we would like to get hostnames by architecture we could compose queries
by doing the following:
```sql
-- name: get_os_by_architecture
-- docs: Gets operative system's name by a given architecture.
SELECT name
FROM operative_system
WHERE architecture = :architecture
-- name: get_hostnames_by_architecture
-- docs: Gets hostnames by architecture.
SELECT hostname
FROM servers
WHERE os_name IN ( :get_os_by_architecture )
```
The previous query would generate the function
`Queries.get_hostnames_by_architecture/2` that can be called as:
```elixir
iex> Queries.get_hostnames_by_architecture(architecture: "AMD64")
{:ok,
[
%{hostname: "server0"},
%{hostname: "server1"},
...
]
}
```
### Optional Fragments
Let's say that now we need to order ascending or descending by hostname by
using an optional `:_order_by` parameter e.g:
```sql
-- name: get_os_by_architecture
-- docs: Gets operative system's name by a given architecture.
SELECT name
FROM operative_system
WHERE architecture = :architecture
-- name: get_hostnames_by_architecture
-- docs: Gets hostnames by architecture.
SELECT hostname
FROM servers
WHERE os_name IN ( :get_os_by_architecture )
:_order_by
-- name: ascending
ORDER BY hostname ASC
-- name: descending
ORDER BY hostname DESC
```
The previous query could be called as before:
```elixir
iex> Queries.get_hostnames_by_architecture(architecture: "AMD64")
{:ok,
[
%{hostname: "Barcelona"},
%{hostname: "Granada"},
%{hostname: "Madrid"},
...
]
}
```
or by order ascending:
```elixir
iex> params = [architecture: "AMD64", _order_by: :ascending]
iex> Queries.get_hostnames_by_architecture(params)
{:ok,
[
%{hostname: "Barcelona"},
%{hostname: "Madrid"},
%{hostname: "Granada"},
...
]
}
```
or descending:
```elixir
iex> params = [architecture: "AMD64", _order_by: :descending]
iex> Queries.get_hostnames_by_architecture(params)
{:ok,
[
%{hostname: "Zaragoza"},
%{hostname: "Madrid"},
%{hostname: "Granada"},
...
]
}
```
> Important: A query can be called by name e.g. `:descending` if it's defined
> in the same SQL file. Otherwise, we need to pass the function instead e.g.
> `Queries.descending/2`
>
> ```elixir
> iex> params = [architecture: "AMD64", _order_by: Queries.descending/2]
> iex> Queries.get_hostnames_by_architecture(params)
> {:ok,
> [
> %{hostname: "Zaragoza"},
> %{hostname: "Madrid"},
> %{hostname: "Granada"},
> ...
> ]
> }
> ```
### IN Statement
Lists in SQL might be tricky. That's why AyeSQL supports a special type for
them e.g:
Let's say we have the following query:
```sql
-- name: get_os_by_hostname
-- docs: Gets hostnames and OS names given a list of hostnames.
SELECT hostname, os_name
FROM servers
WHERE hostname IN (:hostnames)
```
It is possible to do the following:
```elixir
iex> params = [hostnames: {:in, ["server0", "server1", "server2"]}]
iex> Server.get_os_by_hostname(params)
{:ok,
[
%{hostname: "server0", os_name: "Debian Buster"},
%{hostname: "server1", avg_ram: "Windows 10"},
%{hostname: "server2", avg_ram: "Minix 3"}
]
}
```
### Subqueries and Subfragments
Subqueries can be composed directly, as show before, or via the `:inner` tuple
e.g. let's say we need to get the adults order by name in ascending order and
age in descending order:
```sql
-- name: ascending
ASC
-- name: descending
DESC
-- name: by_age
age :order_direction
-- name: by_name
name :order_direction
-- name: get_adults
-- docs: Gets adults.
SELECT name, age
FROM person
WHERE age >= 18
ORDER BY :order_by
```
Then our code in elixir would be:
```elixir
iex> order_by = [
...> by_name: [order_direction: :ascending],
...> by_age: [order_direction: :descending]
...> ]
iex> Queries.get_adults(order_by: {:inner, order_by, ", "})
{:ok,
[
%{name: "Alice", age: 42},
%{name: "Bob", age: 21},
...
]
}
```
> **Note**: If you're using this level of composability and it fits your use
> case, consider using either:
> - [Ecto](https://hexdocs.pm/ecto/Ecto.html)
> - [EEx templates](https://hexdocs.pm/ayesql/dynamic-queries-with-eex.html)
## Installation
AyeSQL is available as a Hex package. To install, add it to your
dependencies in your `mix.exs` file:
```elixir
def deps do
[{:ayesql, "~> 1.1"}]
end
```
If you're going to use any of the provided query runners, then you should add
their dependencies as well:
- Add `:ecto_sql` for `AyeSQL.Runner.Ecto` (default runner).
- Add `:postgrex` for `AyeSQL.Runner.Postgrex`.
- Add `:ecto_sql` and `:postgrex` for running queries using `Ecto` in a
`PostgreSQL` database.
## Author
Alexander de Sousa.
## License
AyeSQL is released under the MIT License. See the LICENSE file for further
details.
