Create RANGE-clause-in-window-functions-practical-examples.md

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RANGE-clause-in-window-functions-practical-examples.md

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+RANGE Clause in Window Functions: Practical Examples
+
+RANGE Clause in Window Functions is now available in Snowflake. 
+
+# Example 1. Running sum of acquitions in the last 28 days
+
+## Input Table: Acquisitions by Date
+
+| A | 3  | 2019-10-11 |
+|---|----|------------|
+| A | 5  | 2019-10-08 |
+| A | 10 | 2019-10-05 |
+| A | 2  | 2019-09-15 |
+| A | 1  | 2019-09-09 |
+| A | 1  | 2019-09-01 |
+| B | 3  | 2019-10-11 |
+| B | 2  | 2019-10-08 |
+| B | 3  | 2019-10-05 |
+| B | 1  | 2019-09-15 |
+| B | 4  | 2019-09-09 |
+| C | 1  | 2019-10-11 |
+| C | 2  | 2019-10-08 |
+| C | 1  | 2019-10-05 |
+| C | 1  | 2019-09-15 |
+| C | 0  | 2019-09-09 |
+| C | 4  | 2019-09-01 |
+| C | 1  | 2019-08-28 |
+
+## RANGE based Window query to get running sum of acquitions in the last 28 days
+
+```sql
+select 
+  *
+  , sum(qty) over (partition by article
+      order by date_acquired
+      range between interval '28 day' preceding and current row
+    ) as sum_qty_28_days
+from acquisitions;
+```
+
+## Query Output:
+
+| A | 1  | 2019-09-01 | 1  |
+|---|----|------------|----|
+| A | 1  | 2019-09-09 | 2  |
+| A | 2  | 2019-09-15 | 4  |
+| A | 10 | 2019-10-05 | 13 |
+| A | 5  | 2019-10-08 | 17 |
+| A | 3  | 2019-10-11 | 20 |
+| C | 1  | 2019-08-28 | 1  |
+| C | 4  | 2019-09-01 | 5  |
+| C | 0  | 2019-09-09 | 5  |
+| C | 1  | 2019-09-15 | 6  |
+| C | 1  | 2019-10-05 | 2  |
+| C | 2  | 2019-10-08 | 4  |
+| C | 1  | 2019-10-11 | 5  |
+| B | 4  | 2019-09-09 | 4  |
+| B | 1  | 2019-09-15 | 5  |
+| B | 3  | 2019-10-05 | 8  |
+| B | 2  | 2019-10-08 | 6  |
+| B | 3  | 2019-10-11 | 9  |