Question

给定具有电话号码的人（表：联系人）（表：电话），

如何编写SQL查询（Sqlite3，postgres或MySQL）来显示每个人及其所有电话号码？

 Table: contacts      Table: Phones
 id  name             id  phone_number    contact_id
 1   Ashok            1   (111) 123-1111  1
 2   Betty            2   (111) 123-2222  1
 3   Charles          3   (111) 123-3333  1
                      4   (111) 123-4444  1
                      5   (222) 456-1111  2
                      6   (222) 456-2222  2
                      7   (333) 789-1111  3
                      8   (333) 789-2222  3
                      9   (333) 789-3333  3

我希望输出为：

Name    Phones
Ashok   (111) 123-1111 (111) 123-2222 (111) 123-3333 (111) 123-4444
Betty   (222) 456-1111 (222) 456-2222 
Charles (333) 789-1111 (333) 789-2222 (333) 789-3333

如果我加入：

SELECT      c.name, p.phone_number
FROM        contacts as c
INNER JOIN  phones as p
ON          c.id = p.contact_id
ORDER BY    c.name

结果不是我想要的：

Name    Phone
Ashok   (111) 123-1111
Ashok   (111) 123-2222
Ashok   (111) 123-3333
Ashok   (111) 123-4444
Betty   (222) 456-1111
Betty   (222) 456-2222
Charles (333) 789-1111
Charles (333) 789-2222
Charles (333) 789-3333

Answer 1

MySQL 和 SQLite 都有GROUP_CONCAT()函数：

SELECT c.name, GROUP_CONCAT(p.phone_number) AS Phones
FROM contacts AS c
INNER JOIN phones AS p ON c.id = p.contact_id
GROUP BY c.name
ORDER BY c.name;

在 PostgreSQL 中，您可以使用array_to_string()和array_agg()函数：

SELECT c.name, array_to_string(array_agg(p.phone_number), ',') AS Phones
FROM contacts AS c
INNER JOIN phones AS p ON c.id = p.contact_id
GROUP BY c.name
ORDER BY c.name;

自 PostgreSQL 9.0以来，您可以直接使用string_agg()：

SELECT c.name, string_agg(p.phone_number, ',') AS Phones
FROM contacts AS c
INNER JOIN phones AS p ON c.id = p.contact_id
GROUP BY c.name
ORDER BY c.name;

SQL用于列出表b中表a的关联数据

1 个答案: