From 4907f96597d6367becb616834ab4efa9fe87717b Mon Sep 17 00:00:00 2001
From: "Rico Sta. Cruz" <rstacruz@users.noreply.github.com>
Date: Mon, 23 Nov 2015 10:43:51 +1100
Subject: [PATCH] arel: add

---
 .projections.json | 10 +++++++++
 arel.md           | 52 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 .projections.json
 create mode 100644 arel.md

diff --git a/.projections.json b/.projections.json
new file mode 100644
index 000000000..8f4e07373
--- /dev/null
+++ b/.projections.json
@@ -0,0 +1,10 @@
+{
+  "*.md": {
+    "type": "cheat",
+    "template": [
+      "---",
+      "title: {basename|capitalize}",
+      "---"
+    ]
+  }
+}
diff --git a/arel.md b/arel.md
new file mode 100644
index 000000000..9acd7c86d
--- /dev/null
+++ b/arel.md
@@ -0,0 +1,52 @@
+---
+title: Arel
+---
+
+### Tables
+
+```rb
+users = Arel::Table.new(:users)
+```
+
+### Fields
+
+```rb
+users[:name]
+users[:id]
+```
+
+### `where` (restriction)
+
+```rb
+users.where(users[:name].eq('amy'))
+# SELECT * FROM users WHERE users.name = 'amy'
+```
+
+### `select` (projection)
+
+```rb
+users.project(users[:id])
+# SELECT users.id FROM users
+```
+
+### `join`
+
+```rb
+users.join(photos)
+users.join(photos, Arel::Nodes::OuterJoin).on(users[:id].eq(photos[:user_id]))
+```
+
+### `limit` / `offset`
+
+```rb
+users.take(5) # => SELECT * FROM users LIMIT 5
+users.skip(4) # => SELECT * FROM users OFFSET 4
+```
+
+### Aggregates
+
+```rb
+users.project(users[:age].sum) # .average .minimum .maximum
+users.project(users[:id].count)
+users.project(users[:id].count.as('user_count'))
+```