统计每个品类有多少个商品。
- 按
category分组，n为该品类的商品行数（即使某些列为 null 也照样计数）。 - 本题数据里
category不会为 null。
输入
products(product_id, name, category, price, cost, launched_on)
输出
列为 category, n，每个品类一行，行顺序不限。
每类商品数
输入表 （case base，共 2 个 case：base、small）
products shop/products
| # | product_idint64 | namestring | categorystring | pricefloat64 | costfloat64 | launched_ondate |
|---|---|---|---|---|---|---|
| 1 | 1 | Wireless Mouse | Electronics | 25.0 | 16.77 | 2025-05-07 |
| 2 | 2 | USB-C Hub | Electronics | 49.9 | 34.17 | 2025-07-27 |
| 3 | 3 | Bluetooth Speaker | Electronics | 89.0 | 61.47 | 2025-02-10 |
| 4 | 4 | Mechanical Keyboard | Electronics | 199.0 | 105.48 | 2024-09-19 |
| 5 | 5 | 4K Monitor | Electronics | 500.0 | 282.38 | 2024-07-10 |
| 6 | 6 | Noise-cancel Headphones | Electronics | 299.0 | 211.57 | 2025-01-14 |
| 7 | 7 | Python Cookbook | Books | 59.0 | 30.08 | 2025-09-15 |
| 8 | 8 | SQL Pocket Guide | Books | 39.9 | 22.14 | 2025-01-20 |
| 9 | 9 | 数据分析实战 | Books | 79.0 | 40.83 | 2024-12-15 |
| 10 | 10 | Clean Code | Books | 50.0 | 28.48 | 2025-03-13 |
| 11 | 11 | 统计学习方法 | Books | 99.0 | 70.22 | 2025-03-13 |
| 12 | 12 | Desk Lamp | Home | 45.0 | 24.99 | 2025-11-04 |
| 13 | 13 | Ceramic Mug | Home | 19.9 | 11.34 | 2025-12-02 |
| 14 | 14 | Throw Pillow | Home | 35.0 | 19.23 | 2024-06-29 |
| 15 | 15 | Wall Clock | Home | 99.0 | 47.98 | 2025-02-23 |
| 16 | 16 | Storage Box | Home | 29.9 | 15.06 | 2025-02-27 |
| 17 | 17 | Puzzle 1000pc | Toys | 129.0 | 59.53 | 2025-08-19 |
| 18 | 18 | Building Blocks | Toys | 199.0 | 110.19 | 2025-04-18 |
| 19 | 19 | RC Car | Toys | 359.0 | 208.55 | 2025-11-06 |
| 20 | 20 | Plush Panda | Toys | 89.0 | 43.14 | 2026-01-12 |
显示前 20 行，共 30 行
期望输出 （case base，行顺序不限）
| # | categoryString | nInt64 |
|---|---|---|
| 1 | Electronics | 6 |
| 2 | Books | 5 |
| 3 | Home | 5 |
| 4 | Toys | 4 |
| 5 | Sports | 5 |
| 6 | Beauty | 5 |
共 6 行