[英]mysql query two row from two tables
我有此查询以调用信息形成两个表。
DB::get("SELECT friends. * , (SELECT `login` FROM `users` WHERE `users`.`id` = friends.`user_id`) AS `login` FROM `friends` WHERE `id_user`='" . $this->user['id'] . "' ORDER BY `id` DESC LIMIT ")
因此,如果用户在朋友列表上,显示用户名,我想获取用户名和头像。 阿凡达行avatar
。 我尝试这个。
DB::get("SELECT friends. * , (SELECT `login`, `*avatar*` FROM `users` WHERE `users`.`id` = friends.`user_id`) AS `login` FROM `friends` WHERE `id_user`='" . $this->user['id'] . "' ORDER BY `id` DESC LIMIT ")
给我错误
SQLSTATE[21000]: Cardinality violation: 1241 Operand should contain 1 column(s)
错误在哪里?
您需要使用JOIN
,例如:
SELECT f.*, u.*
FROM friends f JOIN users u ON f.user_id = u.id
WHERE f.id_user = <your_id>
ORDER BY id DESC LIMIT <your_limit>;
首先,您应该使用Prepared Statement ,其次,您不能编写内联视图,该视图有两列
SELECT friends. * , (SELECT `login`, `*avatar*` FROM ..
相反,您应该使用JOIN
,它可能比当前方法更有效并且更具可读性。
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