From ae6947c7c54a86882ee5d1c6234378596ab06b76 Mon Sep 17 00:00:00 2001
From: "Rico Sta. Cruz" <rstacruz@users.noreply.github.com>
Date: Fri, 27 Nov 2015 00:15:04 +1100
Subject: [PATCH] sql-join: add

---
 sql-join.md | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 sql-join.md

diff --git a/sql-join.md b/sql-join.md
new file mode 100644
index 000000000..5644a5b27
--- /dev/null
+++ b/sql-join.md
@@ -0,0 +1,19 @@
+---
+title: SQL Join
+---
+
+```
+SELECT * FROM order_items LEFT OUTER JOIN orders ON order_items.order_id = orders.id
+```
+
+```
+   __  __
+ /   /\   \
+| A |u |B  |
+ \___\/__ /
+```
+
+* inner join = `u`
+* left outer join = `A` + `u`
+* right outer join = `u` + `B`
+* full outer join = `A` + `u` + `B`