SQL：如何根據公共/私有類別從計數中排除行？

Question

我有兩個表（產品和類別）和一個多對多鏈接表（products_categories）。 我要構建的查詢應該只返回屬於 5 個或更多公共類別的產品。 私有類別在“類別”表的“公共”列中有一個“0”，公共類別有一個“1”。

我找不到忽略計數中的私人類別的方法。 從我的測試數據來看，只有 Shovel 和 Lighter 才能脫穎而出。 目前我得到了摩托車、鏟子、籃球、足球、網球、鎬和打火機，因為它們屬於 5 個或更多類別（公共和私人）。

表格：

CREATE TABLE products(
  id INT NOT NULL AUTO_INCREMENT,  
  name VARCHAR(25),
  price INT,
  created_at DATE,
  PRIMARY KEY(id)
);

CREATE TABLE categories(
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(25),
  public BIT NOT NULL DEFAULT 0,
  PRIMARY KEY (id)
);

CREATE TABLE products_categories(
  product_id INT,
  category_id INT,
  FOREIGN KEY (product_id) REFERENCES products(id),
  FOREIGN KEY (category_id) REFERENCES categories(id)
);

查詢：

SELECT products.id, products.name, COUNT(categories.id)
FROM products
INNER JOIN products_categories ON products.id = products_categories.product_id
INNER JOIN categories ON categories.id = products_categories.category_id
GROUP BY products.id
HAVING COUNT(categories.id) >= 5

測試數據：

INSERT INTO categories VALUES
(1, 'Small', b'1'),
(2, 'Medium', b'1'),
(3, 'Large', b'1'),
(4, 'One-size', b'1'),
(5, 'Tool', b'1'),
(6, 'Sport', b'1'),
(7, 'Ball', b'1'),
(8, 'Camping', b'1'),
(9, 'Food', b'1'),
(10, 'Non-food', b'1'),
(11, 'High-return', b'0'),
(12, 'Low-return', b'0'),
(13, 'Dangerous', b'0');

INSERT INTO products VALUES
(1, 'Bicycle', 50, '2021-03-02'),
(2, 'Motorbike', 100, '2021-03-02'),
(3, 'Shovel', 10, '2021-03-02'),
(4, 'Skis', 20, '2021-03-02'),
(5, 'Tent-S', 20, '2021-03-02'),
(6, 'Tent-M', 30, '2021-03-02'),
(7, 'Tent-L', 30, '2021-03-02'),
(8, 'Basketball', 5, '2021-03-02'),
(9, 'Football', 5, '2021-03-02'),
(10, 'Tennisball', 2, '2021-03-02'),
(11, 'Pickaxe', 15, '2021-03-02'),
(12, 'Lighter', 1, '2021-03-02'),
(13, 'Bottle-S', 2, '2021-03-02'),
(14, 'Bottle-M', 3, '2021-03-02'),
(15, 'Bottle-L', 4, '2021-03-02');

INSERT INTO products_categories VALUES
(1, 4),
(1, 6),
(1, 10),
(1, 11),
(2, 4),
(2, 6),
(2, 10),
(2, 11),
(2, 13),
(3, 4),
(3, 5),
(3, 8),
(3, 10),
(3, 12),
(3, 13),
(4, 4),
(4, 6),
(4, 10),
(4, 11),
(5, 1),
(5, 8),
(5, 10),
(5, 12),
(6, 2),
(6, 8),
(6, 10),
(6, 12),
(7, 3),
(7, 8),
(7, 10),
(7, 12),
(8, 4),
(8, 6),
(8, 7),
(8, 10),
(8, 12),
(9, 4),
(9, 6),
(9, 7),
(9, 10),
(9, 12),
(10, 4),
(10, 6),
(10, 7),
(10, 10),
(10, 12),
(11, 4),
(11, 5),
(11, 10),
(11, 12),
(11, 13),
(12, 4),
(12, 5),
(12, 8),
(12, 10),
(12, 11),
(12, 13),
(13, 1),
(13, 8),
(13, 9),
(13, 12),
(14, 2),
(14, 8),
(14, 9),
(14, 12),
(15, 3),
(15, 8),
(15, 9),
(15, 12);

Answer 1

你似乎想要：

SELECT p.id, p.name, COUNT(*)
FROM products p JOIN
     products_categories pc
     ON p.id = pc.product_id JOIN
     categories c
     ON c.id = pc.category_id
WHERE c.public = 1
GROUP BY p.id, p.name
HAVING COUNT(*) >= 5