Asked  7 Months ago    Answers:  5   Viewed   14 times

Here is the script to create my tables:

CREATE TABLE clients (
   client_i INT(11),
   PRIMARY KEY (client_id)
);
CREATE TABLE projects (
   project_id INT(11) UNSIGNED,
   client_id INT(11) UNSIGNED,
   PRIMARY KEY (project_id)
);
CREATE TABLE posts (
   post_id INT(11) UNSIGNED,
   project_id INT(11) UNSIGNED,
   PRIMARY KEY (post_id)
);

In my PHP code, when deleting a client, I want to delete all projects posts:

DELETE 
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id;

The posts table does not have a foreign key client_id, only project_id. I want to delete the posts in projects that have the passed client_id.

This is not working right now because no posts are deleted.

 Answers

74

You just need to specify that you want to delete the entries from the posts table:

DELETE posts
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id

EDIT: For more information you can see this alternative answer

Tuesday, June 1, 2021
 
innovation
answered 7 Months ago
94

You do not need to do that. You are using prepared statements, which escape the variables automatically.

Wednesday, March 31, 2021
 
laurent
answered 9 Months ago
81

When you use just "localhost" the MySQL client library tries to use a Unix domain socket for the connection instead of a TCP/IP connection. The error is telling you that the socket, called MySQL, cannot be used to make the connection, probably because it does not exist (error number 2).

From the MySQL Documentation:

On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a --port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use --host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server. You can also specify the connection protocol explicitly, even for localhost, by using the --protocol=TCP option.

There are a few ways to solve this problem.

  1. You can just use TCP/IP instead of the Unix socket. You would do this by using 127.0.0.1 instead of localhost when you connect. The Unix socket might by faster and safer to use, though.
  2. You can change the socket in php.ini: open the MySQL configuration file my.cnf to find where MySQL creates the socket, and set PHP's mysqli.default_socket to that path. On my system it's /var/run/mysqld/mysqld.sock.
  3. Configure the socket directly in the PHP script when opening the connection. For example:

    $db = new MySQLi('localhost', 'kamil', '***', '', 0, 
                                  '/var/run/mysqld/mysqld.sock')
    
Tuesday, June 1, 2021
 
Anand
answered 7 Months ago
67

Based on the answer I linked to in my comment above, this should work:

delete from
(
select pf.* From PRODUCTFILTERS pf 
where pf.id>=200 
And pf.rowid in 
  (
     Select rowid from PRODUCTFILTERS 
     inner join PRODUCTS on PRODUCTFILTERS.PRODUCTID = PRODUCTS.ID 
     And PRODUCTS.NAME= 'Mark'
  )
); 

or

delete from PRODUCTFILTERS where rowid in
(
select pf.rowid From PRODUCTFILTERS pf 
where pf.id>=200 
And pf.rowid in 
  (
     Select PRODUCTFILTERS.rowid from PRODUCTFILTERS 
     inner join PRODUCTS on PRODUCTFILTERS.PRODUCTID = PRODUCTS.ID 
     And PRODUCTS.NAME= 'Mark'
  )
); 
Wednesday, July 28, 2021
 
edsk
answered 4 Months ago
85

You can't use LIMIT directly within DELETE when you're referencing multiple tables at the same time, but you can get around that by encasing what you want to delete within a subselect:

DELETE po 
FROM   foro_post po
JOIN   (
       SELECT    p.postid
       FROM      foro_post p
       LEFT JOIN foro_thread t ON p.threadid = t.threadid
       WHERE     t.threadid IS NULL
       ORDER BY  p.postid
       LIMIT     50
       ) pp ON po.postid = pp.postid
Sunday, August 15, 2021
 
Pascal
answered 4 Months ago
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