Create aggregate-mode.md

Author: soyeric128

docs/en/sql-reference/20-sql-functions/07-aggregate-functions/aggregate-mode.md

@@ -0,0 +1,48 @@
+---
+title: MODE
+---
+import FunctionDescription from '@site/src/components/FunctionDescription';
+
+<FunctionDescription description="Introduced or updated: v1.2.647"/>
+
+Returns the value that appears most frequently in a group of values.
+
+## Syntax
+
+```sql
+MODE(<expr>)
+```
+
+## Examples
+
+This example identifies the best-selling product for each month from the sales data:
+
+```sql
+CREATE OR REPLACE TABLE sales (
+    sale_date DATE,
+    product_id INT,
+    quantity INT
+);
+
+INSERT INTO sales (sale_date, product_id, quantity) VALUES
+    ('2024-01-01', 101, 10),
+    ('2024-01-02', 102, 15),
+    ('2024-01-02', 101, 10),
+    ('2024-01-03', 103, 8),
+    ('2024-01-03', 101, 10),
+    ('2024-02-01', 101, 20),
+    ('2024-02-02', 102, 15),
+    ('2024-02-03', 102, 15);
+
+SELECT MONTH(sale_date) AS month, MODE(product_id) AS most_sold_product
+FROM sales
+GROUP BY month
+ORDER BY month;
+
+┌─────────────────────────────────────┐
+│      month      │ most_sold_product │
+├─────────────────┼───────────────────┤
+│               1 │               101 │
+│               2 │               102 │
+└─────────────────────────────────────┘
+```