Select 行有一组特定的项目通过连接 table

Question

假设我们有以下架构：

CREATE TABLE customers(
    id INTEGER PRIMARY KEY, 
    name TEXT
);
CREATE TABLE items(
    id INTEGER PRIMARY KEY, 
    name TEXT
);
CREATE TABLE customers_items(
    customerid INTEGER, 
    itemid INTEGER, 
    FOREIGN KEY(customerid) REFERENCES customers(id),
    FOREIGN KEY(itemid) REFERENCES items(id)
);

现在我们插入一些示例数据：

INSERT INTO customers(name) VALUES ('John');
INSERT INTO customers(name) VALUES ('Jane');

INSERT INTO items(name) VALUES ('duck');
INSERT INTO items(name) VALUES ('cake');

假设 John 和 Jane 的 ID 分别为 1 和 2，duck 和 cake 的 ID 也分别为 1 和 2。让我们给约翰一只鸭子，给简一只鸭子和一个蛋糕。

INSERT INTO customers_items(customerid, itemid) VALUES (1, 1);
INSERT INTO customers_items(customerid, itemid) VALUES (2, 1);
INSERT INTO customers_items(customerid, itemid) VALUES (2, 2);

现在，我想做的是运行两种类型的查询：

Select 既有鸭子又有蛋糕的顾客姓名（只应 return 'Jane'）。
Select 有鸭子但没有蛋糕的顾客的名字（应该 return 'John'）。

Answer 1

对于列出的两种类型的查询，您可以使用 EXISTS 子句。下面是一个使用 exists 子句的示例查询：

SELECT cust.name 
from customers AS cust
WHERE EXISTS (
     SELECT 1
     FROM items
     INNER JOIN customers_items ON items.id = customers_items.itemid
     INNER JOIN customers on customers_items.customerid = cust.id
     WHERE items.name = 'duck')
AND NOT EXISTS (
     SELECT 1
     FROM items
     INNER JOIN customers_items ON items.id = customers_items.itemid
     INNER JOIN customers on customers_items.customerid = cust.id
     WHERE items.name = 'cake')

这是一个工作示例：http://sqlfiddle.com/#!6/3d362/2

Select 行有一组特定的项目通过连接 table

Select rows that have a specific set of items associated with them through a junction table

sql

join

junction-table