mysql在一条语句中从两个表中选择两列

Question

I have been looking if an this has been answered before in SO, but I could not find any.

I have basically two tables in one database. Table member_privileges 1 keeps users reputation, and table 2 keeps user details. They look roughly like this.

mysql> describe member_privileges; 
   +---------------------------+--------------+------+-----+---------+----------------+
        | Field                     | Type         | Null | Key | Default | Extra          |
        +---------------------------+--------------+------+-----+---------+----------------+
        | id                        | int(11)      | NO   | PRI | NULL    | auto_increment |
        | username                  | varchar(255) | YES  |     | NULL    |                |
        | can_comment               | int(11)      | NO   |     | NULL    |                |
        | can_create_articles       | int(11)      | NO   |     | NULL    |                |
        | can_edit_articles         | int(11)      | YES  |     | NULL    |                |
        | can_edit_timeline         | int(11)      | NO   |     | NULL    |                |
        | can_remove_comments       | int(11)      | NO   |     | NULL    |                |
        | can_upload_profile_images | int(11)      | NO   |     | NULL    |                |
        | can_upload_article_images | int(11)      | NO   |     | NULL    |                |
        | can_approve_new_articles  | int(11)      | NO   |     | NULL    |                |
        | can_freez_articles        | int(11)      | NO   |     | NULL    |                |
        +---------------------------+--------------+------+-----+---------+----------------+

and this is the users table.

mysql> describe users;
+----------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+----------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| username       | varchar(255) | NO   |     | NULL    |                |
| password       | varchar(255) | NO   |     | NULL    |                |
| age            | int(11)      | NO   |     | NULL    |                |
| country        | varchar(255) | NO   |     | NULL    |                |
| email          | varchar(255) | NO   |     | NULL    |                |
| link           | varchar(255) | NO   |     | NULL    |                |
| reg_date       | date         | YES  |     | NULL    |                |
| ip             | varchar(255) | YES  |     | NULL    |                |
| gender         | varchar(10)  | YES  |     | NULL    |                |
| about          | varchar(255) | YES  |     | NULL    |                |
| is_activated   | int(11)      | YES  |     | NULL    |                |
| activation_key | varchar(255) | YES  |     | NULL    |                |
| image_path     | varchar(255) | YES  |     | NULL    |                |
+----------------+--------------+------+-----+---------+----------------+

So, in one page for example, I am trying to check if user 'john' has a can_edit_articles permission set. So, if in member_privileges a username "john" has a can_edit_articles set to 1, then that user can edit.

The problem is checking those details at one. Unlike running two queries like I am doing it now.

$email = $_SESSION['email']; 

$get_user = "SELECT id, username FROM members WHERE email = $email; 

$can_user_edit = "SELECT can_edit_articles FROM member_privileges WHERE $email = ?;

So, as you can see I am running two queries, and I would like to know if there is any way to run those within one mysql statement. ...

Answer 1

Use an inner join and prevent your sql statements from sql injection

If you would like to select the id, username and can_edit_articles values:

"SELECT m.id, m.username, p.can_edit_articles  
 FROM members m inner join member_privileges p  
 ON m.username=p.username WHERE m.email = '$email'"

Answer 2

You should use JOIN in your query. Like this:

SELECT can_edit_articles FROM member_privileges 
P LEFT JOIN  members M ON P.username = M.username WHERE email = '$email' 

Answer 3

$email = $_SESSION['email']; 

$can_user_edit = "SELECT can_edit_articles FROM member_privileges  
                  WHERE username = (SELECT username FROM users WHERE email = '$email')";