Question

I have 2 tables in my MySQL table: cat and notes.

MySQL for cat

CREATE TABLE IF NOT EXISTS `cat` (
  `cat_id` int(11) NOT NULL AUTO_INCREMENT,
  `cname` int(11) NOT NULL,
  PRIMARY KEY (`cat_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

MySQL for notes:

CREATE TABLE IF NOT EXISTS `notes` (
  `notes_id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(50) NOT NULL,
  `notebody` varchar(300) NOT NULL,
  `cat_id` int(20) NOT NULL,
  `approved` int(11) NOT NULL,
  PRIMARY KEY (`notes_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

I like to know how to count how many notes each category have that approved equals to 1. and I want to show categories that have zero notes as category name – 0. I tried left join but it’s leaving all categories that have zero notes.

Answer 1

Try

SELECT cat_id, COUNT(*) AS cnt
FROM notes
WHERE approved = 1
GROUP BY cat_id

And

SELECT c.cat_id, c.cname, COUNT(*) AS cnt
FROM cat c
LEFT OUTER JOIN notes n ON n.cat_id = c.cat_id
GROUP BY c.cat_id
HAVING cnt < 1