我有这个架构可以使用:
-- store messages between users
CREATE TABLE chat_messages (
id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
sender_id BIGINT UNSIGNED NOT NULL,
recipient_id BIGINT UNSIGNED NOT NULL,
message_body TEXT,
read_at DATETIME DEFAULT NULL,
created_at DATETIME NOT NULL,
PRIMARY KEY(id),
CONSTRAINT FK_messages_1 FOREIGN KEY (sender_id) REFERENCES profiles (id),
CONSTRAINT FK_messages_2 FOREIGN KEY (recipient_id) REFERENCES profiles (id)
) ENGINE = INNODB;
我需要对其运行查询以获取用户的唯一事件聊天列表,我有以下查询:
SELECT * FROM chat_messages WHERE recipient_id = :user_id GROUP BY recipient_id ORDER BY created_at DESC
但是,这会返回分组行:
返回的行包含 message_body,但它不是最新消息(按照需要按先前排序的数据集对其进行分组的思路进行思考)
此外,如果用户向另一个用户发送消息但尚未收到回复,则不会将其包含在列表中(在这种情况下,还应考虑 sender_id)
有什么建议可以通过以性能为中心的查询来实现这一切吗?谢谢:)
最佳答案
您可以使用 notists
查询执行您想要的操作:
SELECT cm.*
FROM chat_messages cm
WHERE recipient_id = :user_id AND
NOT EXISTS (SELECT 1
FROM chat_messages cm2
WHERE cm2.recipient_id = cm.recipient_id AND
cm2.created_at > cm.created_at
)
ORDER BY created_at DESC;
为了提高性能,您应该在 chat_messages(recipient_id,created_at)
上建立索引。
关于mysql一对一消息优化表查询,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23793771/