Question

1）如果给定的邮件ID与其邮件ID匹配，则从3（学生，教师，校友）表访问密码

2）我只想为这三个用户编写一个密码恢复程序

从一个表中访问一个密码的代码是

 select password from current_student where mail_Id='"+mail_Id+"'

另一个代码

(SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM current_student HAVING mail_Id = 'mahender0791@gmail.com') UNION (SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM dept_Staff HAVING mail_Id = 'mahender0791@gmail.com') UNION (SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM  alumni HAVING mail_Id = 'mahender0791@gmail.com')

，错误消息是

Query: (select password as r_password,mail_Id as r_mail_Id from current_student HAVING mail_Id = 'mahender0791@gmail.com') UNION (selec...

Error Code: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'HAVING mail_Id = 'mahender0791@gmail.com') 
 LIMIT 0, 1000' at line 1

Answer 1

可能是这样的：

(SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id FROM current_student HAVING r_mail_Id = 'mahender0791@gmail.com') UNION
(SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id FROM dept_Staff HAVING r_mail_Id = 'mahender0791@gmail.com') UNION
(SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id FROM YOUR_TABLE_NAME HAVING r_mail_Id = 'mahender0791@gmail.com')

YOUR_TABLE_NAME＆gt;＆gt;使用相应的表名更改此表名。

Answer 2

(SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM current_student HAVING r_mail_Id = 'xx') UNION (SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM dept_Staff HAVING r_mail_Id = 'xx') UNION (SELECT PASSWORD AS r_password,mail_Id AS r_mail_Id  FROM alumni HAVING r_mail_Id = 'xx')

这将起作用

数据查询可能性？

2 个答案: