Question

I have a users table.
I have a certifications table.

Each user can have multiple certifications. Certifications has a user_id foreign key.

1. How may I select a user as well as all of their certifications in one query?
2. How may I select users that have certifications?

users table:

CREATE TABLE `users` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `username` varchar(24) default NULL,
  `displayname` varchar(24) default NULL,
  `email` varchar(64) default NULL,
  `password` text,
  `signup_date` int(11) default NULL,
  `signup_ip` varchar(15) default NULL,
  `hash` text,
  `verified` tinyint(1) default '0',
  `last_login` int(11) default NULL,
  `logins` int(11) default NULL,
  `status` text,
  `recovery_hash` text,
  `recovery_initiated` int(11) default NULL,
  `last_updated` int(11) default NULL,
  `signup_method` text,
  `signup_question` int(11) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

certifications table:

CREATE TABLE `certifications` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `user_id` int(11) unsigned NOT NULL,
  `number` varchar(128) default NULL,
  `board` varchar(128) default NULL,
  `company` varchar(128) default NULL,
  `website` varchar(128) default NULL,
  PRIMARY KEY  (`id`),
  KEY `user_id` (`user_id`),
  CONSTRAINT `certifications_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

Thank you for reading.

Answer 1

How may I select a user as well as all of their certifications in one query?

SELECT *
FROM certifivations C
LEFT JOIN users U
ON C.user_id = U.id
WHERE U.id=USERID

How may I select users that have certifications?

SELECT *
FROM certifivations C
JOIN users U
ON C.user_id = U.id
GROUP BY U.id