Question

因此，我无法解决以下问题。给出了三个表：tables

我需要使用join编写代码，以便所有对朋友对均以其全名列出。我只知道可能需要两个联接，其中之一是自我联接。我试图将一个persons表与friends表连接起来，但是一栏中的结果是name，另一列是and id，我不知道如何进行两个连续的联接，以便每个名字都有一个对应的朋友的名字。这是表格信息：

CREATE TABLE persons (
id INTEGER PRIMARY KEY AUTOINCREMENT,
fullname TEXT,
age INTEGER);



INSERT INTO persons (fullname, age) VALUES ("Bobby McBobbyFace", "12");
INSERT INTO persons (fullname, age) VALUES ("Lucy BoBucie", "25");
INSERT INTO persons (fullname, age) VALUES ("Banana FoFanna", "14");
INSERT INTO persons (fullname, age) VALUES ("Shish Kabob", "20");

CREATE table hobbies (
id INTEGER PRIMARY KEY AUTOINCREMENT,
person_id INTEGER,
name TEXT);

INSERT INTO hobbies (person_id, name) VALUES (1, "drawing");
INSERT INTO hobbies (person_id, name) VALUES (2, "dancing");
INSERT INTO hobbies (person_id, name) VALUES (3, "skating");
INSERT INTO hobbies (person_id, name) VALUES (4, "coding");

CREATE table friends (
id INTEGER PRIMARY KEY AUTOINCREMENT,
person1_id INTEGER,
person2_id INTEGER);

INSERT INTO friends (person1_id, person2_id)
VALUES (1, 4);
INSERT INTO friends (person1_id, person2_id)
VALUES (2, 3);

Answer 1

您是否正在寻找两个联接？

select p1.fullname, p2.fullname
from friends f join
     persons p1
     on f.person1_id = p1.id join
     persons p2
     on f.person2_id = p2.id;

找不到有关三个表和联接操作的问题的解决方案

1 个答案: