店主想把东西多的分类摆在门口。按 category 分组数每类几样,只留下超过 2 样的分类。结果两列:分类,几样。
| id | name | category | price | stock |
|---|---|---|---|---|
| 1 | Milk tea | drink | 12 | 30 |
| 2 | Lemon water | drink | 8 | 50 |
| 3 | Cheesecake | cake | 25 | 6 |
| 4 | Cookie | snack | 5 | 80 |
| 5 | Brownie | cake | 18 | 0 |
| 6 | Iced coffee | drink | 15 | 20 |
| 7 | Chips | snack | 7 | 40 |
| 8 | Fruit tart | cake | 28 | 4 |
| id | name | category | price | stock |
|---|---|---|---|---|
| 1 | Milk tea | drink | 12 | 30 |
| 2 | Lemon water | drink | 8 | 50 |
| 3 | Cheesecake | cake | 25 | 6 |
| 4 | Cookie | snack | 5 | 80 |
| 5 | Brownie | cake | 18 | 0 |
| 6 | Iced coffee | drink | 15 | 20 |
| 7 | Chips | snack | 7 | 40 |
| 8 | Fruit tart | cake | 28 | 4 |
SELECT category, COUNT(*) FROM products GROUP BY category -- 在这里写:用 HAVING 留下 COUNT(*) 大于 2 的组 ;
写好了先点「运行」看看结果,没问题再点「提交」。