Question

我有一个被称为联系人的地址簿。为了帮助组织联系我有团体（例如家人，朋友，工作）。我想说，每组显示4或10个联系人示例。这适用于列出所有组的组索引页面，但不打算每个组具有完整的联系人列表（仅适用于专用组页面）。

组表和列

email_groups

id，id_user，name

通讯录表格和列

email_contacts

id，id_group，id_user，name

我一直在努力解决这个问题，但c1的列名错误。

SELECT 
eg.id, 
eg.name, 
(SELECT c1.name FROM email_contacts AS c1 WHERE id_user='1' LIMIT 0,1) AS contact_1, 
(SELECT c2.name FROM email_contacts AS c1 WHERE id_user='1' LIMIT 1,1) AS contact_2, 
(SELECT c3.name FROM email_contacts AS c3 WHERE id_user='1' LIMIT 2,1) AS contact_3, 
(SELECT c4.name FROM email_contacts AS c4 WHERE id_user='1' LIMIT 3,1) AS contact_4 
FROM email_groups AS eg 
INNER JOIN email_contacts AS ec on ec.id=eg.id_group

Answer 1

您已在子查询中提供了两次别名C1，我猜第二个子查询将为C2，您尝试选择c2.name，但您提供的别名为{{ 1}} SELECT c2.name FROM email_contacts AS c1

c1

显示所有联系人组时，MySQL显示有限数量的联系人

1 个答案: