sql-join: update

sql-join.md

@@ -1,20 +1,31 @@
 ---
-title: SQL Join
+title: SQL joins
+layout: 2017/sheet
+updated: 2017-10-30
+weight: -1
 ---
 
+### Example
+
 ```
 SELECT * FROM order_items LEFT OUTER JOIN orders ON order_items.order_id = orders.id
 ```
+{: .-wrap}
+
+### Diagram
 
 ```
-.--------.
+┌────────┐
-| A  .---+----.
+│ A  ┌───┼────┐
-|    | ∩ |    |
+│    │ ∩ │    │
-'----+---'  B |
+└────┼───┘  B │
-     '--------'
+     └────────┘
 ```
+{: .-box-chars}
 
-* inner join = `∩`
+| Join             | What            |
-* left outer join = `A` + `∩`
+| ----             | ----            |
-* right outer join = `∩` + `B`
+| Inner join       | `∩`             |
-* full outer join = `A` + `∩` + `B`
+| Left outer join  | `A` + `∩`       |
+| Right outer join | `∩` + `B`       |
+| Full outer join  | `A` + `∩` + `B` |