Question

如何从多个表中选择记录

表“用户”： user_id |用户名|电子邮件|登录|密码

表“ users_log” log_id | user_id |状态|时间戳|消息

表“ users_balance” balance_id | user_id |状态|金额

表“ users_roles” role_id |状态|角色名称

表“ users_role” role_id | user_id

如何通过用户电子邮件以及日志状态和用户角色来检索所有记录

Answer 1

您可以使用 JOIN 查询从多个表中获取数据

请尝试一下

SELECT usr.*,usrlg.*,usrbl.*,usrrl.*,usrrls.* FROM users AS usr JOIN users_log AS usrlg ON(usrlg.user_id=usr.user_id) JOIN users_balance AS usrbl ON (usrbl.user_id=usr.user_id)
JOIN users_role AS usrrl ON(usrrl.user_id=usr.user_id) JOIN users_roles AS usrrls ON(usrrls.role_id=usrrl.role_id)
 WHERE usr.email='value' AND usrlg.status='value' AND usrrls.role_name='value'

Answer 2

我猜是这样的。

SELECT 
 log.timestamp AS log_timestamp, 
 u.user_id, 
 u.username AS user_name, 
 u.email AS user_email,
 role.name AS role_name,
 bal.amount AS balance_amount,
 log.message AS log_message
FROM users AS u 
JOIN users_role AS ur ON ur.user_id = u.user_id
JOIN users_roles AS role ON role.role_id = ur.role_id
JOIN users_log AS log ON u.user_id = log.user_id
LEFT JOIN users_balance AS bal ON bal.user_id = u.user_id
WHERE u.email = @UserEmail
  AND role.role_name = @RoleName
  AND log.status = @LogStatus

然后用您要查找的内容设置或替换@ UserEmail，@ RoleName，@ LogStatus变量。

但是根据数据，您可能想要添加GROUP BY和aggregate function，例如MAX或SUM，并可能在WHERE或HAVING子句中添加其他条件。

Answer 3

您可以通过联接来实现。可以参考下面的链接。

https://www.guru99.com/joins.html

http://www.mysqltutorial.org/mysql-join/

https://www.tutorialspoint.com/mysql/mysql-using-joins.htm

从MySQL中的多个表中检索记录

3 个答案: